CHAPTER X ELECTRIC TELEGRAPHSExperiments in telegraphy were carried out as far back as the year 1753, when it was proposed to transmit messages by representing the letters of the alphabet by combinations of sparks produced by a static machine; but these were of little practical value and nothing of any importance was accomplished until after the discovery of galvanic current.Many of these old experiments were very crude and appear somewhat ridiculous when compared with the methods of nowadays. The earliest proposal for an electric telegraph appeared in theScots’ Magazinefor February, 1753, and shows several kinds of proposed telegraphs acting by the attractive power of electricity, conveyed by a series of parallel wires, one wire corresponding to each letter of the alphabet and supported by glass rods at every twenty yards. Words were to be spelled by the action of the electricity in attracting paper letters, or by striking bells corresponding to letters.The modern telegraph consists essentially of four things, namely:A battery which produces an electric current.A wire which conducts the electric current from one point to another.A transmitter for shutting the current off and on.An electro-magnetic receiving apparatus, which gives out in sounds, the signals made by the pulsations of the current from a distant point.The battery may be almost any form of battery. Gravity cells are preferred, however, for telegraph work.Heavy galvanized iron wire is usually employed as the "line." It is necessary to use non-conductors wherever the wire is fastened. Glass insulators placed on a wooden pin or bracket, which is fastened to the pole or building on which the wire is to be supported, are used for outside work. Inside of buildings, rubber tubes are used where the wires pass through walls, etc.The operation of a telegraph is not, as many people suppose, a complicated or difficult matter to understand, but is quite simple.The key is a contrivance for controlling the passage of the electric current in much the same manner as an ordinary switch. It consists of a steel lever, swung on trunnion-screws mounted in a frame, and provided with a rubber knob which the operator grasps lightly with the thumb and forefinger. On pressing the lever downward, a platinum point fastened on the under side of the lever is brought into contact with another point set into a rubber bushing in the base of the key, so that there is no electrical connection between the two points unless the key is pressed down or "closed," as it is often termed. The key is usually fastened to the operating bench by two rods called "legs." The lever is provided with screws which permit the stroke of the key to be very closely adjusted.Fig. 130.—A Typical Telegraph Key, showing the Various Parts.Fig. 130.—A Typical Telegraph Key, showing the Various Parts.The line wire and battery are connected to the key, so that no current can flow until the key is pressed and the contacts brought together.A "sounder" consists of two electromagnets mounted on a base under a movable flat piece of iron which is attracted by the magnetism of the electromagnets when a current flows through them and is withdrawn by a spring when no magnetism excites the windings.This piece of iron, which is called the armature, is mounted upon a strip of brass or aluminum called the lever. The lever strikes against a brass "anvil" and produces the "clicks," which form the dots and dashes of the telegraph alphabet.Fig. 131.—A Typical Telegraph Sounder, showing the Various Parts.Fig. 131.—A Typical Telegraph Sounder, showing the Various Parts.Every time that the key is pressed, an electric current is sent out into the line. The current flows through the magnets of the sounder and causes the armature to be drawn downward. The lever strikes the anvil and produces a "click." When the key lever is released, the current is shut up and the lever flies up and clicks against the top of the anvil.The period of time between the first click and the second click may be varied at will according to the length of time that the key is held down. A short period is called adotand a long period adash. Combinations of dots, dashes, and spaces arranged according to the Morse Alphabet, make intelligible signals.How To Make a Simple Key and SounderThe little telegraph instruments shown in Figures 132 and 133 are not practical for long lines but may be used for ticking messages from one room to another, and can be made the source of much instruction and pleasure.Fig. 132.—A Simple Home-made Telegraph Key.Fig. 132.—A Simple Home-made Telegraph Key.The key is a strip of brass fastened to a wooden base in the manner shown in Figure 132. It is fitted with a knob of some sort on the front end, so that it is conveniently gripped with the fingers.The little bridge is made from heavy sheet-brass and prevents the lever from moving too far away from the contact on the upward stroke.Connections are made to the key lever at the back end and the contact in front by the binding-posts,AandB. The post,C, connects with the bridge.The sounder consists of two small electromagnets mounted in a vertical position on a wooden base. The magnets are connected at the bottom by a strip of heavy sheet-iron which acts as a yoke.Fig. 133.—A Simple Home-made Telegraph Sounder.Fig. 133.—A Simple Home-made Telegraph Sounder.The armature is made out of sheet-iron, rolled up in the manner shown in the illustration. One end of the armature is fastened to a wooden block in such a position that the armature comes directly over the magnets and about one-eighth of an inch above them. The opposite end of the armature moves up and down for about an eighth of an inch between two screws, each fastened in a wooden block mounted on an upright board in the back of the magnets. The purpose of the screws is to make the "click" of the sounder louder and clearer than it would be if the armature only struck the wood.A rubber band or a small wire spring passing over a screw and connected at the other end to the armature will draw the latter away from the magnets when the current is not passing.The terminals of the magnets are connected to binding-posts mounted on the base.Fig. 134.—A Diagram showing how to connect two Simple Telegraph Stations.Fig. 134.—A Diagram showing how to connect two Simple Telegraph Stations.The key and sounder should be placed in series with one or two cells of a battery. Pressing the key will then cause the armature of the sounder to be drawn down and make a click. When the key is released, the armature will be drawn up by the spring or rubber band and make a second click.Hardly a boy interested in mechanics and electricity has not at some time or other wished for a telegraph instrument with which to put up a "line" with his chum.A practical working set of such instruments can be very easily constructed, and with little expense, by following the sketches and instructions given here.The magnets for the sounder may either be constructed by the intending telegraph operator or secured from some old electrical instrument such as a magneto-bell. In the latter case, the hardest part of the work will be avoided.If they are to be home-made, the following suggestions may prove of value in carrying out their construction.Fig. 135.—A Complete Telegraph Set, consisting of a Keyboard and a Sounder.Fig. 135.—A Complete Telegraph Set, consisting of a Keyboard and a Sounder.The cores are made from one-quarter-inch stove-bolts with the heads cut off. The magnet heads are cut out of hard-wood fiber, one-eighth of an inch thick and one inch in diameter. They should fit tightly and be held in place with glue. They are separated so as to form a winding space between of seven-eighths of an inch. The magnets should be wound full of No. 25 B. & S. gauge cotton-covered wire.Fig. 136.—Details of the Telegraph Set shown in Figure 135.Fig. 136.—Details of the Telegraph Set shown in Figure 135.The yoke is made of enough strips of sheet-iron, one-half inch wide and two inches long, to form a pile one-quarter of an inch thick. Two one-quarter-inch holes are bored in the opposite ends of the yoke, one and one-half inches apart. The lower ends of the magnet cores are passed through these holes. The ends should project one-half of an inch beyond the yoke.They are passed through two holes in a base-board three-quarters of an inch thick. The holes are countersunk from the lower side, so that a nut can be screwed on the lower end of each and the magnets held tightly in an upright position. The remaining parts of the instrument are very easily made, and are so clearly shown by the drawing that it is hardly necessary to say more than a few words in explanation.The lever or tongue, the anvil, the standard, and the lever of the key are all cut out of hard-wood according to the pattern shown in the illustration.The armature is a piece of soft iron fastened to the lever with a small brass screw.Tacks are placed under the heads of the adjusting screws on the sounder so that it will click more loudly.The rubber band acts as a spring to counteract the weight of the armature and lever and draw it up as soon as the current is cut off. The movement of the lever should be so adjusted that it is only sufficient to make an audible click.Use care to avoid friction between the lever and the standard, so that the former will move with perfect freedom.All the screws used in the work should be round-headed brass wood screws with the points filed flat. Bore a small hole before screwing them into place so as to avoid splitting the wood.The construction of the key is even more simple than that of the sounder. It should move up and down without any side motion.The circuit-closer should be kept closed when the instruments are not in use, and when you are receiving a message. As soon as you are through receiving and wish to transmit, you should open your circuit-closer and your friend close his.The tension of the spring under the lever of the key must be adjusted to suit the needs of each individual operator.Fig. 137.—A Diagram showing how to connect two Complete Telegraph Sets, using one Line Wire and a Ground.Fig. 137.—A Diagram showing how to connect two Complete Telegraph Sets, using one Line Wire and a Ground. The Two-Point Switches throw the Batteries out of Circuit when the Line is not in use.The diagram for connecting the instruments is self-explanatory. In cities or towns where a "ground" is available by connecting to the gas or water pipes, one line wire may be easily dispensed with. Or, if desirable, a ground may be formed by burying a large plate of zinc (three or four feet square) in a moist spot and leading the wire to it.How To Build a Telegraph RelayIn working a telegraph over a long line or where there are a large number of instruments on one circuit, the currents are often not strong enough to work the sounder directly. In such a case arelayis used. The relay is built on the same principle as a sounder, but the parts are made much lighter, so that the instrument is more sensitive. The armature of a relay is so small and its movement so little that its clicking is scarcely audible. It is therefore fitted with a second set of contacts and connected to a battery and a sounder, which is to set in operation every time the contacts close. The principle of a relay is that a weak current of insufficient strength to do the work itself may set a strong local current to do its work for it.There are many forms of relays, and while that which is described below is not of the type commonly used on telegraph lines, it has the advantage of being far more sensitive than any instrument of the regular line relay type that the average experimenter could build.Fig. 138.—Details of the Relay Parts.Fig. 138.—Details of the Relay Parts.Make the magnets from one-quarter-inch stove-bolts, and cut them off so that they will form a core about two and one-quarter inches long. Fit each of the cores with two fiber heads to hold the wire in place. Insulate the legs with paper and wind each with about fifty layers of No. 30 B. & S. gauge single-cotton-covered magnet wire. The winding space between the magnet’s heads should be one and one-eighth inches.The upper ends of the magnet cores should be allowed to project about one-quarter of an inch beyond the fiber head. The end of the core is filed flat, as shown in the illustration.The magnets are mounted upon an iron yoke, three-sixteenths of an inch thick. The holes in the yoke should be spaced so that there is a distance of one and one-half inches between the centers of the magnet cores.The armature of the relay is mounted on a small steel shaft with sharp points at each end. The exact shape of the armature may be best understood from the illustrations.The lower end of the shaft rests in a small cone-shaped depression made by driving a center punch into the yoke half-way between the two magnets.The top bearing is a strip of brass projecting from a wooden support. The end of the shaft rests in a depression similar to that in the yoke.The contact lever is made of brass and forced on the shaft below the armature. It swings between a small brass clip fastened to one side of the support and a little screw held in a similar clip on the opposite side.The contact clip is made of spring brass about No. 22 gauge in thickness. It may be adjusted by a screw passing through the support.The armature may be controlled in its movement so that the latter will be very slight by adjusting the screws.There should not be any friction in the bearings and the armature should move with perfect freedom. The armature should approach the ends of the magnet cores until a space about the thickness of heavy paper separates them and should not touch them.Fig. 139.—The Completed Relay.Fig. 139.—The Completed Relay.The spring is made of fine brass wire. It is fastened to the armature shaft, and the screw mounted on the wooden support with a piece of silk thread. The thread is passed around the shaft once or twice so that the tension of the spring will cause the armature to move away from the pole pieces just as soon as the current flowing through the magnets ceases.Fig. 140.—A Diagram showing how to connect a Relay, Sounder, and Key.Fig. 140.—A Diagram showing how to connect a Relay, Sounder, and Key. Closing the Key will operate the Relay. The Relay will then operate the Sounder in turn.The tension of the spring may be adjusted by turning the screw with a screw-driver. If the armature tends to stick to the magnet poles fasten a small piece of paper to the poles with some shellac.The terminals of the magnets are connected to two binding-posts markedAandB. The binding-posts markedCandDare connected respectively to the contact clip and the brass bearing on the top of the wooden support.The diagram in Figure 140 shows how the relay is connected to a telegraph line.How To Learn To TelegraphThe instruments so far described have been practical working telegraph instruments, but they lack the fine points of commercial apparatus and it is not possible to become as efficient an operator with their aid as with a real key and sounder.If the young experimenter desires to become a proficient telegraph operator, the first thing to do is to purchase a Learner’s telegraph key and sounder.Connect a dry cell to the binding-posts on the back of the instrument. Screw the set down on a table about eighteen inches from the front edge, so that there is plenty of room for the arm to rest. See that none of the various adjustment screws about the instrument are loose and that the armature of the sounder moves freely up and down through a distance of about one-sixteenth of an inch.The spring which draws the lever upwards away from the magnets should be set only at sufficient tension to raise the lever when no current is passing. If too tight, the spring will not allow the armature to respond to the current flowing through the magnets.The key is provided with several adjustment-screws to regulate the tension and the play of the lever to suit the hand of the operator. A little practice will enable the student to judge best for himself just how the key should be set.The next step is to memorize the alphabet, so that each character can instantly be called to mind at will. The punctuation marks are not used very frequently, and the period is the only one which the student need learn at first.The Morse alphabet consists of dots, dashes, and spaces. Combinations of these signals spell letters and words.Many of the characters are the reverse of others. For example,Ais the reverse ofN.BandF,DandU,CandR,QandX,Zand&, are the other reverse letters, so if the formation of one of each of these letters is memorized the reverse is easily mastered.It is important that the beginner should learn how properly to grasp the key, for habits are easily formed and a poor position will limit the sending speed of the operator.Place the first or index finger on the top of the key-handle, with the thumb under the edge; and the second finger on the opposite side. The fingers should be curved so as to form a quarter-section of a circle. Bring the third and fourth fingers down so that they are almost closed on the palm of the hand. Rest the arm on the table in front of the key and allow the wrist to be perfectly limber.Fig. 141.—How to hold a Telegraph Key.Fig. 141.—How to hold a Telegraph Key.The grasp on the key should be firm but not rigid. Avoid using too much strength or a light hesitating touch. Endeavor to acquire a positive, firm up and down motion of the key. Avoid all side pressure, and do not allow the fingers to leave the key when making the signals. The movement is made principally with the wrist, with the fingers and hand perfectly elastic.A dot is made by a single instantaneous, downward stroke of the key. A dash is made by holding the key down for the same period of time that it takes to make three dots. A long dash is made by holding the key down for the same time that it takes to make five dots.A space in the letters, such as, for instance, the space between the first and last two dots in the letterRshould occupy the time of one dot. The space between each letter should occupy the time required for two dots, and the space between words should occupy the time required for three dots.Commence the use of the key by making dots in succession, first at the rate of two every second, and increasing the speed until ten can be made. Practice should be continued until three hundred and sixty dots a minute can be made with perfect regularity.Then begin making dashes at the rate of two every three seconds, and continue until one hundred and twenty a minute can be made with perfect regularity.Practise the long dashes at the rate of one a second, and increase until ninety can be made in a minute.Fig. 142.—The Morse Telegraphic Code.Fig. 142.—The Morse Telegraphic Code.When this has been accomplished, practise the following letters until they can be perfectly made. Each row of letters is an exercise which should be practised separately until mastered.Dot LettersE I S H P 6Dot and Space LettersO C R Y Z &Dash LettersT L M 5 ODots and DashesA U V 4Dashes and DotsN D B 8Mixed Dots and DashesF G J K Q W X 1 2 3 7 9 PeriodAfter you can write these different letters, practise making words. Select a list of commonly used words. When words seem easy to write, practise sending pages from a book.Systematic and continual practice will enable the student to make surprising progress in mastering the art of sending.Reading and receiving messages must be practised with a companion student. Place two instruments in separate rooms or in separate houses so that the operators will be entirely dependent upon the instruments for their communication with each other. Start by transmitting and receiving simple messages. Then use pages from a book, and increase the speed until it is possible to send and receive at least 15 words a minute without watching the sounder but merely depending upon the clicks to determine the duration of the dots and dashes.Figure 140 shows how to arrange a regular telegraph line for two stations. Gravity batteries should be used for regular telegraph work. It is necessary that the key should be kept closed by having its circuit-closer shut when messages are not being sent. If one of the keys is left open the circuit is broken, and it is not possible for a person at the other end of the line to send a message.Every telegraph office has a name or call usually consisting of two letters; thus for New York the call might be N. Y. and for Chicago, C. H.If New York should desire to call Chicago, he would repeat the call letters, C H., until answered. Chicago would answer by sending I, several times and signing, C H. When so answered, New York would proceed with the message.MICROPHONES AND TELEPHONES
CHAPTER X ELECTRIC TELEGRAPHSExperiments in telegraphy were carried out as far back as the year 1753, when it was proposed to transmit messages by representing the letters of the alphabet by combinations of sparks produced by a static machine; but these were of little practical value and nothing of any importance was accomplished until after the discovery of galvanic current.Many of these old experiments were very crude and appear somewhat ridiculous when compared with the methods of nowadays. The earliest proposal for an electric telegraph appeared in theScots’ Magazinefor February, 1753, and shows several kinds of proposed telegraphs acting by the attractive power of electricity, conveyed by a series of parallel wires, one wire corresponding to each letter of the alphabet and supported by glass rods at every twenty yards. Words were to be spelled by the action of the electricity in attracting paper letters, or by striking bells corresponding to letters.The modern telegraph consists essentially of four things, namely:A battery which produces an electric current.A wire which conducts the electric current from one point to another.A transmitter for shutting the current off and on.An electro-magnetic receiving apparatus, which gives out in sounds, the signals made by the pulsations of the current from a distant point.The battery may be almost any form of battery. Gravity cells are preferred, however, for telegraph work.Heavy galvanized iron wire is usually employed as the "line." It is necessary to use non-conductors wherever the wire is fastened. Glass insulators placed on a wooden pin or bracket, which is fastened to the pole or building on which the wire is to be supported, are used for outside work. Inside of buildings, rubber tubes are used where the wires pass through walls, etc.The operation of a telegraph is not, as many people suppose, a complicated or difficult matter to understand, but is quite simple.The key is a contrivance for controlling the passage of the electric current in much the same manner as an ordinary switch. It consists of a steel lever, swung on trunnion-screws mounted in a frame, and provided with a rubber knob which the operator grasps lightly with the thumb and forefinger. On pressing the lever downward, a platinum point fastened on the under side of the lever is brought into contact with another point set into a rubber bushing in the base of the key, so that there is no electrical connection between the two points unless the key is pressed down or "closed," as it is often termed. The key is usually fastened to the operating bench by two rods called "legs." The lever is provided with screws which permit the stroke of the key to be very closely adjusted.Fig. 130.—A Typical Telegraph Key, showing the Various Parts.Fig. 130.—A Typical Telegraph Key, showing the Various Parts.The line wire and battery are connected to the key, so that no current can flow until the key is pressed and the contacts brought together.A "sounder" consists of two electromagnets mounted on a base under a movable flat piece of iron which is attracted by the magnetism of the electromagnets when a current flows through them and is withdrawn by a spring when no magnetism excites the windings.This piece of iron, which is called the armature, is mounted upon a strip of brass or aluminum called the lever. The lever strikes against a brass "anvil" and produces the "clicks," which form the dots and dashes of the telegraph alphabet.Fig. 131.—A Typical Telegraph Sounder, showing the Various Parts.Fig. 131.—A Typical Telegraph Sounder, showing the Various Parts.Every time that the key is pressed, an electric current is sent out into the line. The current flows through the magnets of the sounder and causes the armature to be drawn downward. The lever strikes the anvil and produces a "click." When the key lever is released, the current is shut up and the lever flies up and clicks against the top of the anvil.The period of time between the first click and the second click may be varied at will according to the length of time that the key is held down. A short period is called adotand a long period adash. Combinations of dots, dashes, and spaces arranged according to the Morse Alphabet, make intelligible signals.How To Make a Simple Key and SounderThe little telegraph instruments shown in Figures 132 and 133 are not practical for long lines but may be used for ticking messages from one room to another, and can be made the source of much instruction and pleasure.Fig. 132.—A Simple Home-made Telegraph Key.Fig. 132.—A Simple Home-made Telegraph Key.The key is a strip of brass fastened to a wooden base in the manner shown in Figure 132. It is fitted with a knob of some sort on the front end, so that it is conveniently gripped with the fingers.The little bridge is made from heavy sheet-brass and prevents the lever from moving too far away from the contact on the upward stroke.Connections are made to the key lever at the back end and the contact in front by the binding-posts,AandB. The post,C, connects with the bridge.The sounder consists of two small electromagnets mounted in a vertical position on a wooden base. The magnets are connected at the bottom by a strip of heavy sheet-iron which acts as a yoke.Fig. 133.—A Simple Home-made Telegraph Sounder.Fig. 133.—A Simple Home-made Telegraph Sounder.The armature is made out of sheet-iron, rolled up in the manner shown in the illustration. One end of the armature is fastened to a wooden block in such a position that the armature comes directly over the magnets and about one-eighth of an inch above them. The opposite end of the armature moves up and down for about an eighth of an inch between two screws, each fastened in a wooden block mounted on an upright board in the back of the magnets. The purpose of the screws is to make the "click" of the sounder louder and clearer than it would be if the armature only struck the wood.A rubber band or a small wire spring passing over a screw and connected at the other end to the armature will draw the latter away from the magnets when the current is not passing.The terminals of the magnets are connected to binding-posts mounted on the base.Fig. 134.—A Diagram showing how to connect two Simple Telegraph Stations.Fig. 134.—A Diagram showing how to connect two Simple Telegraph Stations.The key and sounder should be placed in series with one or two cells of a battery. Pressing the key will then cause the armature of the sounder to be drawn down and make a click. When the key is released, the armature will be drawn up by the spring or rubber band and make a second click.Hardly a boy interested in mechanics and electricity has not at some time or other wished for a telegraph instrument with which to put up a "line" with his chum.A practical working set of such instruments can be very easily constructed, and with little expense, by following the sketches and instructions given here.The magnets for the sounder may either be constructed by the intending telegraph operator or secured from some old electrical instrument such as a magneto-bell. In the latter case, the hardest part of the work will be avoided.If they are to be home-made, the following suggestions may prove of value in carrying out their construction.Fig. 135.—A Complete Telegraph Set, consisting of a Keyboard and a Sounder.Fig. 135.—A Complete Telegraph Set, consisting of a Keyboard and a Sounder.The cores are made from one-quarter-inch stove-bolts with the heads cut off. The magnet heads are cut out of hard-wood fiber, one-eighth of an inch thick and one inch in diameter. They should fit tightly and be held in place with glue. They are separated so as to form a winding space between of seven-eighths of an inch. The magnets should be wound full of No. 25 B. & S. gauge cotton-covered wire.Fig. 136.—Details of the Telegraph Set shown in Figure 135.Fig. 136.—Details of the Telegraph Set shown in Figure 135.The yoke is made of enough strips of sheet-iron, one-half inch wide and two inches long, to form a pile one-quarter of an inch thick. Two one-quarter-inch holes are bored in the opposite ends of the yoke, one and one-half inches apart. The lower ends of the magnet cores are passed through these holes. The ends should project one-half of an inch beyond the yoke.They are passed through two holes in a base-board three-quarters of an inch thick. The holes are countersunk from the lower side, so that a nut can be screwed on the lower end of each and the magnets held tightly in an upright position. The remaining parts of the instrument are very easily made, and are so clearly shown by the drawing that it is hardly necessary to say more than a few words in explanation.The lever or tongue, the anvil, the standard, and the lever of the key are all cut out of hard-wood according to the pattern shown in the illustration.The armature is a piece of soft iron fastened to the lever with a small brass screw.Tacks are placed under the heads of the adjusting screws on the sounder so that it will click more loudly.The rubber band acts as a spring to counteract the weight of the armature and lever and draw it up as soon as the current is cut off. The movement of the lever should be so adjusted that it is only sufficient to make an audible click.Use care to avoid friction between the lever and the standard, so that the former will move with perfect freedom.All the screws used in the work should be round-headed brass wood screws with the points filed flat. Bore a small hole before screwing them into place so as to avoid splitting the wood.The construction of the key is even more simple than that of the sounder. It should move up and down without any side motion.The circuit-closer should be kept closed when the instruments are not in use, and when you are receiving a message. As soon as you are through receiving and wish to transmit, you should open your circuit-closer and your friend close his.The tension of the spring under the lever of the key must be adjusted to suit the needs of each individual operator.Fig. 137.—A Diagram showing how to connect two Complete Telegraph Sets, using one Line Wire and a Ground.Fig. 137.—A Diagram showing how to connect two Complete Telegraph Sets, using one Line Wire and a Ground. The Two-Point Switches throw the Batteries out of Circuit when the Line is not in use.The diagram for connecting the instruments is self-explanatory. In cities or towns where a "ground" is available by connecting to the gas or water pipes, one line wire may be easily dispensed with. Or, if desirable, a ground may be formed by burying a large plate of zinc (three or four feet square) in a moist spot and leading the wire to it.How To Build a Telegraph RelayIn working a telegraph over a long line or where there are a large number of instruments on one circuit, the currents are often not strong enough to work the sounder directly. In such a case arelayis used. The relay is built on the same principle as a sounder, but the parts are made much lighter, so that the instrument is more sensitive. The armature of a relay is so small and its movement so little that its clicking is scarcely audible. It is therefore fitted with a second set of contacts and connected to a battery and a sounder, which is to set in operation every time the contacts close. The principle of a relay is that a weak current of insufficient strength to do the work itself may set a strong local current to do its work for it.There are many forms of relays, and while that which is described below is not of the type commonly used on telegraph lines, it has the advantage of being far more sensitive than any instrument of the regular line relay type that the average experimenter could build.Fig. 138.—Details of the Relay Parts.Fig. 138.—Details of the Relay Parts.Make the magnets from one-quarter-inch stove-bolts, and cut them off so that they will form a core about two and one-quarter inches long. Fit each of the cores with two fiber heads to hold the wire in place. Insulate the legs with paper and wind each with about fifty layers of No. 30 B. & S. gauge single-cotton-covered magnet wire. The winding space between the magnet’s heads should be one and one-eighth inches.The upper ends of the magnet cores should be allowed to project about one-quarter of an inch beyond the fiber head. The end of the core is filed flat, as shown in the illustration.The magnets are mounted upon an iron yoke, three-sixteenths of an inch thick. The holes in the yoke should be spaced so that there is a distance of one and one-half inches between the centers of the magnet cores.The armature of the relay is mounted on a small steel shaft with sharp points at each end. The exact shape of the armature may be best understood from the illustrations.The lower end of the shaft rests in a small cone-shaped depression made by driving a center punch into the yoke half-way between the two magnets.The top bearing is a strip of brass projecting from a wooden support. The end of the shaft rests in a depression similar to that in the yoke.The contact lever is made of brass and forced on the shaft below the armature. It swings between a small brass clip fastened to one side of the support and a little screw held in a similar clip on the opposite side.The contact clip is made of spring brass about No. 22 gauge in thickness. It may be adjusted by a screw passing through the support.The armature may be controlled in its movement so that the latter will be very slight by adjusting the screws.There should not be any friction in the bearings and the armature should move with perfect freedom. The armature should approach the ends of the magnet cores until a space about the thickness of heavy paper separates them and should not touch them.Fig. 139.—The Completed Relay.Fig. 139.—The Completed Relay.The spring is made of fine brass wire. It is fastened to the armature shaft, and the screw mounted on the wooden support with a piece of silk thread. The thread is passed around the shaft once or twice so that the tension of the spring will cause the armature to move away from the pole pieces just as soon as the current flowing through the magnets ceases.Fig. 140.—A Diagram showing how to connect a Relay, Sounder, and Key.Fig. 140.—A Diagram showing how to connect a Relay, Sounder, and Key. Closing the Key will operate the Relay. The Relay will then operate the Sounder in turn.The tension of the spring may be adjusted by turning the screw with a screw-driver. If the armature tends to stick to the magnet poles fasten a small piece of paper to the poles with some shellac.The terminals of the magnets are connected to two binding-posts markedAandB. The binding-posts markedCandDare connected respectively to the contact clip and the brass bearing on the top of the wooden support.The diagram in Figure 140 shows how the relay is connected to a telegraph line.How To Learn To TelegraphThe instruments so far described have been practical working telegraph instruments, but they lack the fine points of commercial apparatus and it is not possible to become as efficient an operator with their aid as with a real key and sounder.If the young experimenter desires to become a proficient telegraph operator, the first thing to do is to purchase a Learner’s telegraph key and sounder.Connect a dry cell to the binding-posts on the back of the instrument. Screw the set down on a table about eighteen inches from the front edge, so that there is plenty of room for the arm to rest. See that none of the various adjustment screws about the instrument are loose and that the armature of the sounder moves freely up and down through a distance of about one-sixteenth of an inch.The spring which draws the lever upwards away from the magnets should be set only at sufficient tension to raise the lever when no current is passing. If too tight, the spring will not allow the armature to respond to the current flowing through the magnets.The key is provided with several adjustment-screws to regulate the tension and the play of the lever to suit the hand of the operator. A little practice will enable the student to judge best for himself just how the key should be set.The next step is to memorize the alphabet, so that each character can instantly be called to mind at will. The punctuation marks are not used very frequently, and the period is the only one which the student need learn at first.The Morse alphabet consists of dots, dashes, and spaces. Combinations of these signals spell letters and words.Many of the characters are the reverse of others. For example,Ais the reverse ofN.BandF,DandU,CandR,QandX,Zand&, are the other reverse letters, so if the formation of one of each of these letters is memorized the reverse is easily mastered.It is important that the beginner should learn how properly to grasp the key, for habits are easily formed and a poor position will limit the sending speed of the operator.Place the first or index finger on the top of the key-handle, with the thumb under the edge; and the second finger on the opposite side. The fingers should be curved so as to form a quarter-section of a circle. Bring the third and fourth fingers down so that they are almost closed on the palm of the hand. Rest the arm on the table in front of the key and allow the wrist to be perfectly limber.Fig. 141.—How to hold a Telegraph Key.Fig. 141.—How to hold a Telegraph Key.The grasp on the key should be firm but not rigid. Avoid using too much strength or a light hesitating touch. Endeavor to acquire a positive, firm up and down motion of the key. Avoid all side pressure, and do not allow the fingers to leave the key when making the signals. The movement is made principally with the wrist, with the fingers and hand perfectly elastic.A dot is made by a single instantaneous, downward stroke of the key. A dash is made by holding the key down for the same period of time that it takes to make three dots. A long dash is made by holding the key down for the same time that it takes to make five dots.A space in the letters, such as, for instance, the space between the first and last two dots in the letterRshould occupy the time of one dot. The space between each letter should occupy the time required for two dots, and the space between words should occupy the time required for three dots.Commence the use of the key by making dots in succession, first at the rate of two every second, and increasing the speed until ten can be made. Practice should be continued until three hundred and sixty dots a minute can be made with perfect regularity.Then begin making dashes at the rate of two every three seconds, and continue until one hundred and twenty a minute can be made with perfect regularity.Practise the long dashes at the rate of one a second, and increase until ninety can be made in a minute.Fig. 142.—The Morse Telegraphic Code.Fig. 142.—The Morse Telegraphic Code.When this has been accomplished, practise the following letters until they can be perfectly made. Each row of letters is an exercise which should be practised separately until mastered.Dot LettersE I S H P 6Dot and Space LettersO C R Y Z &Dash LettersT L M 5 ODots and DashesA U V 4Dashes and DotsN D B 8Mixed Dots and DashesF G J K Q W X 1 2 3 7 9 PeriodAfter you can write these different letters, practise making words. Select a list of commonly used words. When words seem easy to write, practise sending pages from a book.Systematic and continual practice will enable the student to make surprising progress in mastering the art of sending.Reading and receiving messages must be practised with a companion student. Place two instruments in separate rooms or in separate houses so that the operators will be entirely dependent upon the instruments for their communication with each other. Start by transmitting and receiving simple messages. Then use pages from a book, and increase the speed until it is possible to send and receive at least 15 words a minute without watching the sounder but merely depending upon the clicks to determine the duration of the dots and dashes.Figure 140 shows how to arrange a regular telegraph line for two stations. Gravity batteries should be used for regular telegraph work. It is necessary that the key should be kept closed by having its circuit-closer shut when messages are not being sent. If one of the keys is left open the circuit is broken, and it is not possible for a person at the other end of the line to send a message.Every telegraph office has a name or call usually consisting of two letters; thus for New York the call might be N. Y. and for Chicago, C. H.If New York should desire to call Chicago, he would repeat the call letters, C H., until answered. Chicago would answer by sending I, several times and signing, C H. When so answered, New York would proceed with the message.MICROPHONES AND TELEPHONES
CHAPTER X ELECTRIC TELEGRAPHSExperiments in telegraphy were carried out as far back as the year 1753, when it was proposed to transmit messages by representing the letters of the alphabet by combinations of sparks produced by a static machine; but these were of little practical value and nothing of any importance was accomplished until after the discovery of galvanic current.Many of these old experiments were very crude and appear somewhat ridiculous when compared with the methods of nowadays. The earliest proposal for an electric telegraph appeared in theScots’ Magazinefor February, 1753, and shows several kinds of proposed telegraphs acting by the attractive power of electricity, conveyed by a series of parallel wires, one wire corresponding to each letter of the alphabet and supported by glass rods at every twenty yards. Words were to be spelled by the action of the electricity in attracting paper letters, or by striking bells corresponding to letters.The modern telegraph consists essentially of four things, namely:A battery which produces an electric current.A wire which conducts the electric current from one point to another.A transmitter for shutting the current off and on.An electro-magnetic receiving apparatus, which gives out in sounds, the signals made by the pulsations of the current from a distant point.The battery may be almost any form of battery. Gravity cells are preferred, however, for telegraph work.Heavy galvanized iron wire is usually employed as the "line." It is necessary to use non-conductors wherever the wire is fastened. Glass insulators placed on a wooden pin or bracket, which is fastened to the pole or building on which the wire is to be supported, are used for outside work. Inside of buildings, rubber tubes are used where the wires pass through walls, etc.The operation of a telegraph is not, as many people suppose, a complicated or difficult matter to understand, but is quite simple.The key is a contrivance for controlling the passage of the electric current in much the same manner as an ordinary switch. It consists of a steel lever, swung on trunnion-screws mounted in a frame, and provided with a rubber knob which the operator grasps lightly with the thumb and forefinger. On pressing the lever downward, a platinum point fastened on the under side of the lever is brought into contact with another point set into a rubber bushing in the base of the key, so that there is no electrical connection between the two points unless the key is pressed down or "closed," as it is often termed. The key is usually fastened to the operating bench by two rods called "legs." The lever is provided with screws which permit the stroke of the key to be very closely adjusted.Fig. 130.—A Typical Telegraph Key, showing the Various Parts.Fig. 130.—A Typical Telegraph Key, showing the Various Parts.The line wire and battery are connected to the key, so that no current can flow until the key is pressed and the contacts brought together.A "sounder" consists of two electromagnets mounted on a base under a movable flat piece of iron which is attracted by the magnetism of the electromagnets when a current flows through them and is withdrawn by a spring when no magnetism excites the windings.This piece of iron, which is called the armature, is mounted upon a strip of brass or aluminum called the lever. The lever strikes against a brass "anvil" and produces the "clicks," which form the dots and dashes of the telegraph alphabet.Fig. 131.—A Typical Telegraph Sounder, showing the Various Parts.Fig. 131.—A Typical Telegraph Sounder, showing the Various Parts.Every time that the key is pressed, an electric current is sent out into the line. The current flows through the magnets of the sounder and causes the armature to be drawn downward. The lever strikes the anvil and produces a "click." When the key lever is released, the current is shut up and the lever flies up and clicks against the top of the anvil.The period of time between the first click and the second click may be varied at will according to the length of time that the key is held down. A short period is called adotand a long period adash. Combinations of dots, dashes, and spaces arranged according to the Morse Alphabet, make intelligible signals.How To Make a Simple Key and SounderThe little telegraph instruments shown in Figures 132 and 133 are not practical for long lines but may be used for ticking messages from one room to another, and can be made the source of much instruction and pleasure.Fig. 132.—A Simple Home-made Telegraph Key.Fig. 132.—A Simple Home-made Telegraph Key.The key is a strip of brass fastened to a wooden base in the manner shown in Figure 132. It is fitted with a knob of some sort on the front end, so that it is conveniently gripped with the fingers.The little bridge is made from heavy sheet-brass and prevents the lever from moving too far away from the contact on the upward stroke.Connections are made to the key lever at the back end and the contact in front by the binding-posts,AandB. The post,C, connects with the bridge.The sounder consists of two small electromagnets mounted in a vertical position on a wooden base. The magnets are connected at the bottom by a strip of heavy sheet-iron which acts as a yoke.Fig. 133.—A Simple Home-made Telegraph Sounder.Fig. 133.—A Simple Home-made Telegraph Sounder.The armature is made out of sheet-iron, rolled up in the manner shown in the illustration. One end of the armature is fastened to a wooden block in such a position that the armature comes directly over the magnets and about one-eighth of an inch above them. The opposite end of the armature moves up and down for about an eighth of an inch between two screws, each fastened in a wooden block mounted on an upright board in the back of the magnets. The purpose of the screws is to make the "click" of the sounder louder and clearer than it would be if the armature only struck the wood.A rubber band or a small wire spring passing over a screw and connected at the other end to the armature will draw the latter away from the magnets when the current is not passing.The terminals of the magnets are connected to binding-posts mounted on the base.Fig. 134.—A Diagram showing how to connect two Simple Telegraph Stations.Fig. 134.—A Diagram showing how to connect two Simple Telegraph Stations.The key and sounder should be placed in series with one or two cells of a battery. Pressing the key will then cause the armature of the sounder to be drawn down and make a click. When the key is released, the armature will be drawn up by the spring or rubber band and make a second click.Hardly a boy interested in mechanics and electricity has not at some time or other wished for a telegraph instrument with which to put up a "line" with his chum.A practical working set of such instruments can be very easily constructed, and with little expense, by following the sketches and instructions given here.The magnets for the sounder may either be constructed by the intending telegraph operator or secured from some old electrical instrument such as a magneto-bell. In the latter case, the hardest part of the work will be avoided.If they are to be home-made, the following suggestions may prove of value in carrying out their construction.Fig. 135.—A Complete Telegraph Set, consisting of a Keyboard and a Sounder.Fig. 135.—A Complete Telegraph Set, consisting of a Keyboard and a Sounder.The cores are made from one-quarter-inch stove-bolts with the heads cut off. The magnet heads are cut out of hard-wood fiber, one-eighth of an inch thick and one inch in diameter. They should fit tightly and be held in place with glue. They are separated so as to form a winding space between of seven-eighths of an inch. The magnets should be wound full of No. 25 B. & S. gauge cotton-covered wire.Fig. 136.—Details of the Telegraph Set shown in Figure 135.Fig. 136.—Details of the Telegraph Set shown in Figure 135.The yoke is made of enough strips of sheet-iron, one-half inch wide and two inches long, to form a pile one-quarter of an inch thick. Two one-quarter-inch holes are bored in the opposite ends of the yoke, one and one-half inches apart. The lower ends of the magnet cores are passed through these holes. The ends should project one-half of an inch beyond the yoke.They are passed through two holes in a base-board three-quarters of an inch thick. The holes are countersunk from the lower side, so that a nut can be screwed on the lower end of each and the magnets held tightly in an upright position. The remaining parts of the instrument are very easily made, and are so clearly shown by the drawing that it is hardly necessary to say more than a few words in explanation.The lever or tongue, the anvil, the standard, and the lever of the key are all cut out of hard-wood according to the pattern shown in the illustration.The armature is a piece of soft iron fastened to the lever with a small brass screw.Tacks are placed under the heads of the adjusting screws on the sounder so that it will click more loudly.The rubber band acts as a spring to counteract the weight of the armature and lever and draw it up as soon as the current is cut off. The movement of the lever should be so adjusted that it is only sufficient to make an audible click.Use care to avoid friction between the lever and the standard, so that the former will move with perfect freedom.All the screws used in the work should be round-headed brass wood screws with the points filed flat. Bore a small hole before screwing them into place so as to avoid splitting the wood.The construction of the key is even more simple than that of the sounder. It should move up and down without any side motion.The circuit-closer should be kept closed when the instruments are not in use, and when you are receiving a message. As soon as you are through receiving and wish to transmit, you should open your circuit-closer and your friend close his.The tension of the spring under the lever of the key must be adjusted to suit the needs of each individual operator.Fig. 137.—A Diagram showing how to connect two Complete Telegraph Sets, using one Line Wire and a Ground.Fig. 137.—A Diagram showing how to connect two Complete Telegraph Sets, using one Line Wire and a Ground. The Two-Point Switches throw the Batteries out of Circuit when the Line is not in use.The diagram for connecting the instruments is self-explanatory. In cities or towns where a "ground" is available by connecting to the gas or water pipes, one line wire may be easily dispensed with. Or, if desirable, a ground may be formed by burying a large plate of zinc (three or four feet square) in a moist spot and leading the wire to it.How To Build a Telegraph RelayIn working a telegraph over a long line or where there are a large number of instruments on one circuit, the currents are often not strong enough to work the sounder directly. In such a case arelayis used. The relay is built on the same principle as a sounder, but the parts are made much lighter, so that the instrument is more sensitive. The armature of a relay is so small and its movement so little that its clicking is scarcely audible. It is therefore fitted with a second set of contacts and connected to a battery and a sounder, which is to set in operation every time the contacts close. The principle of a relay is that a weak current of insufficient strength to do the work itself may set a strong local current to do its work for it.There are many forms of relays, and while that which is described below is not of the type commonly used on telegraph lines, it has the advantage of being far more sensitive than any instrument of the regular line relay type that the average experimenter could build.Fig. 138.—Details of the Relay Parts.Fig. 138.—Details of the Relay Parts.Make the magnets from one-quarter-inch stove-bolts, and cut them off so that they will form a core about two and one-quarter inches long. Fit each of the cores with two fiber heads to hold the wire in place. Insulate the legs with paper and wind each with about fifty layers of No. 30 B. & S. gauge single-cotton-covered magnet wire. The winding space between the magnet’s heads should be one and one-eighth inches.The upper ends of the magnet cores should be allowed to project about one-quarter of an inch beyond the fiber head. The end of the core is filed flat, as shown in the illustration.The magnets are mounted upon an iron yoke, three-sixteenths of an inch thick. The holes in the yoke should be spaced so that there is a distance of one and one-half inches between the centers of the magnet cores.The armature of the relay is mounted on a small steel shaft with sharp points at each end. The exact shape of the armature may be best understood from the illustrations.The lower end of the shaft rests in a small cone-shaped depression made by driving a center punch into the yoke half-way between the two magnets.The top bearing is a strip of brass projecting from a wooden support. The end of the shaft rests in a depression similar to that in the yoke.The contact lever is made of brass and forced on the shaft below the armature. It swings between a small brass clip fastened to one side of the support and a little screw held in a similar clip on the opposite side.The contact clip is made of spring brass about No. 22 gauge in thickness. It may be adjusted by a screw passing through the support.The armature may be controlled in its movement so that the latter will be very slight by adjusting the screws.There should not be any friction in the bearings and the armature should move with perfect freedom. The armature should approach the ends of the magnet cores until a space about the thickness of heavy paper separates them and should not touch them.Fig. 139.—The Completed Relay.Fig. 139.—The Completed Relay.The spring is made of fine brass wire. It is fastened to the armature shaft, and the screw mounted on the wooden support with a piece of silk thread. The thread is passed around the shaft once or twice so that the tension of the spring will cause the armature to move away from the pole pieces just as soon as the current flowing through the magnets ceases.Fig. 140.—A Diagram showing how to connect a Relay, Sounder, and Key.Fig. 140.—A Diagram showing how to connect a Relay, Sounder, and Key. Closing the Key will operate the Relay. The Relay will then operate the Sounder in turn.The tension of the spring may be adjusted by turning the screw with a screw-driver. If the armature tends to stick to the magnet poles fasten a small piece of paper to the poles with some shellac.The terminals of the magnets are connected to two binding-posts markedAandB. The binding-posts markedCandDare connected respectively to the contact clip and the brass bearing on the top of the wooden support.The diagram in Figure 140 shows how the relay is connected to a telegraph line.How To Learn To TelegraphThe instruments so far described have been practical working telegraph instruments, but they lack the fine points of commercial apparatus and it is not possible to become as efficient an operator with their aid as with a real key and sounder.If the young experimenter desires to become a proficient telegraph operator, the first thing to do is to purchase a Learner’s telegraph key and sounder.Connect a dry cell to the binding-posts on the back of the instrument. Screw the set down on a table about eighteen inches from the front edge, so that there is plenty of room for the arm to rest. See that none of the various adjustment screws about the instrument are loose and that the armature of the sounder moves freely up and down through a distance of about one-sixteenth of an inch.The spring which draws the lever upwards away from the magnets should be set only at sufficient tension to raise the lever when no current is passing. If too tight, the spring will not allow the armature to respond to the current flowing through the magnets.The key is provided with several adjustment-screws to regulate the tension and the play of the lever to suit the hand of the operator. A little practice will enable the student to judge best for himself just how the key should be set.The next step is to memorize the alphabet, so that each character can instantly be called to mind at will. The punctuation marks are not used very frequently, and the period is the only one which the student need learn at first.The Morse alphabet consists of dots, dashes, and spaces. Combinations of these signals spell letters and words.Many of the characters are the reverse of others. For example,Ais the reverse ofN.BandF,DandU,CandR,QandX,Zand&, are the other reverse letters, so if the formation of one of each of these letters is memorized the reverse is easily mastered.It is important that the beginner should learn how properly to grasp the key, for habits are easily formed and a poor position will limit the sending speed of the operator.Place the first or index finger on the top of the key-handle, with the thumb under the edge; and the second finger on the opposite side. The fingers should be curved so as to form a quarter-section of a circle. Bring the third and fourth fingers down so that they are almost closed on the palm of the hand. Rest the arm on the table in front of the key and allow the wrist to be perfectly limber.Fig. 141.—How to hold a Telegraph Key.Fig. 141.—How to hold a Telegraph Key.The grasp on the key should be firm but not rigid. Avoid using too much strength or a light hesitating touch. Endeavor to acquire a positive, firm up and down motion of the key. Avoid all side pressure, and do not allow the fingers to leave the key when making the signals. The movement is made principally with the wrist, with the fingers and hand perfectly elastic.A dot is made by a single instantaneous, downward stroke of the key. A dash is made by holding the key down for the same period of time that it takes to make three dots. A long dash is made by holding the key down for the same time that it takes to make five dots.A space in the letters, such as, for instance, the space between the first and last two dots in the letterRshould occupy the time of one dot. The space between each letter should occupy the time required for two dots, and the space between words should occupy the time required for three dots.Commence the use of the key by making dots in succession, first at the rate of two every second, and increasing the speed until ten can be made. Practice should be continued until three hundred and sixty dots a minute can be made with perfect regularity.Then begin making dashes at the rate of two every three seconds, and continue until one hundred and twenty a minute can be made with perfect regularity.Practise the long dashes at the rate of one a second, and increase until ninety can be made in a minute.Fig. 142.—The Morse Telegraphic Code.Fig. 142.—The Morse Telegraphic Code.When this has been accomplished, practise the following letters until they can be perfectly made. Each row of letters is an exercise which should be practised separately until mastered.Dot LettersE I S H P 6Dot and Space LettersO C R Y Z &Dash LettersT L M 5 ODots and DashesA U V 4Dashes and DotsN D B 8Mixed Dots and DashesF G J K Q W X 1 2 3 7 9 PeriodAfter you can write these different letters, practise making words. Select a list of commonly used words. When words seem easy to write, practise sending pages from a book.Systematic and continual practice will enable the student to make surprising progress in mastering the art of sending.Reading and receiving messages must be practised with a companion student. Place two instruments in separate rooms or in separate houses so that the operators will be entirely dependent upon the instruments for their communication with each other. Start by transmitting and receiving simple messages. Then use pages from a book, and increase the speed until it is possible to send and receive at least 15 words a minute without watching the sounder but merely depending upon the clicks to determine the duration of the dots and dashes.Figure 140 shows how to arrange a regular telegraph line for two stations. Gravity batteries should be used for regular telegraph work. It is necessary that the key should be kept closed by having its circuit-closer shut when messages are not being sent. If one of the keys is left open the circuit is broken, and it is not possible for a person at the other end of the line to send a message.Every telegraph office has a name or call usually consisting of two letters; thus for New York the call might be N. Y. and for Chicago, C. H.If New York should desire to call Chicago, he would repeat the call letters, C H., until answered. Chicago would answer by sending I, several times and signing, C H. When so answered, New York would proceed with the message.MICROPHONES AND TELEPHONES
Experiments in telegraphy were carried out as far back as the year 1753, when it was proposed to transmit messages by representing the letters of the alphabet by combinations of sparks produced by a static machine; but these were of little practical value and nothing of any importance was accomplished until after the discovery of galvanic current.
Many of these old experiments were very crude and appear somewhat ridiculous when compared with the methods of nowadays. The earliest proposal for an electric telegraph appeared in theScots’ Magazinefor February, 1753, and shows several kinds of proposed telegraphs acting by the attractive power of electricity, conveyed by a series of parallel wires, one wire corresponding to each letter of the alphabet and supported by glass rods at every twenty yards. Words were to be spelled by the action of the electricity in attracting paper letters, or by striking bells corresponding to letters.
The modern telegraph consists essentially of four things, namely:
A battery which produces an electric current.
A wire which conducts the electric current from one point to another.
A transmitter for shutting the current off and on.
An electro-magnetic receiving apparatus, which gives out in sounds, the signals made by the pulsations of the current from a distant point.
The battery may be almost any form of battery. Gravity cells are preferred, however, for telegraph work.
Heavy galvanized iron wire is usually employed as the "line." It is necessary to use non-conductors wherever the wire is fastened. Glass insulators placed on a wooden pin or bracket, which is fastened to the pole or building on which the wire is to be supported, are used for outside work. Inside of buildings, rubber tubes are used where the wires pass through walls, etc.
The operation of a telegraph is not, as many people suppose, a complicated or difficult matter to understand, but is quite simple.
The key is a contrivance for controlling the passage of the electric current in much the same manner as an ordinary switch. It consists of a steel lever, swung on trunnion-screws mounted in a frame, and provided with a rubber knob which the operator grasps lightly with the thumb and forefinger. On pressing the lever downward, a platinum point fastened on the under side of the lever is brought into contact with another point set into a rubber bushing in the base of the key, so that there is no electrical connection between the two points unless the key is pressed down or "closed," as it is often termed. The key is usually fastened to the operating bench by two rods called "legs." The lever is provided with screws which permit the stroke of the key to be very closely adjusted.
Fig. 130.—A Typical Telegraph Key, showing the Various Parts.Fig. 130.—A Typical Telegraph Key, showing the Various Parts.
Fig. 130.—A Typical Telegraph Key, showing the Various Parts.
The line wire and battery are connected to the key, so that no current can flow until the key is pressed and the contacts brought together.
A "sounder" consists of two electromagnets mounted on a base under a movable flat piece of iron which is attracted by the magnetism of the electromagnets when a current flows through them and is withdrawn by a spring when no magnetism excites the windings.
This piece of iron, which is called the armature, is mounted upon a strip of brass or aluminum called the lever. The lever strikes against a brass "anvil" and produces the "clicks," which form the dots and dashes of the telegraph alphabet.
Fig. 131.—A Typical Telegraph Sounder, showing the Various Parts.Fig. 131.—A Typical Telegraph Sounder, showing the Various Parts.
Fig. 131.—A Typical Telegraph Sounder, showing the Various Parts.
Every time that the key is pressed, an electric current is sent out into the line. The current flows through the magnets of the sounder and causes the armature to be drawn downward. The lever strikes the anvil and produces a "click." When the key lever is released, the current is shut up and the lever flies up and clicks against the top of the anvil.
The period of time between the first click and the second click may be varied at will according to the length of time that the key is held down. A short period is called adotand a long period adash. Combinations of dots, dashes, and spaces arranged according to the Morse Alphabet, make intelligible signals.
How To Make a Simple Key and SounderThe little telegraph instruments shown in Figures 132 and 133 are not practical for long lines but may be used for ticking messages from one room to another, and can be made the source of much instruction and pleasure.Fig. 132.—A Simple Home-made Telegraph Key.Fig. 132.—A Simple Home-made Telegraph Key.The key is a strip of brass fastened to a wooden base in the manner shown in Figure 132. It is fitted with a knob of some sort on the front end, so that it is conveniently gripped with the fingers.The little bridge is made from heavy sheet-brass and prevents the lever from moving too far away from the contact on the upward stroke.Connections are made to the key lever at the back end and the contact in front by the binding-posts,AandB. The post,C, connects with the bridge.The sounder consists of two small electromagnets mounted in a vertical position on a wooden base. The magnets are connected at the bottom by a strip of heavy sheet-iron which acts as a yoke.Fig. 133.—A Simple Home-made Telegraph Sounder.Fig. 133.—A Simple Home-made Telegraph Sounder.The armature is made out of sheet-iron, rolled up in the manner shown in the illustration. One end of the armature is fastened to a wooden block in such a position that the armature comes directly over the magnets and about one-eighth of an inch above them. The opposite end of the armature moves up and down for about an eighth of an inch between two screws, each fastened in a wooden block mounted on an upright board in the back of the magnets. The purpose of the screws is to make the "click" of the sounder louder and clearer than it would be if the armature only struck the wood.A rubber band or a small wire spring passing over a screw and connected at the other end to the armature will draw the latter away from the magnets when the current is not passing.The terminals of the magnets are connected to binding-posts mounted on the base.Fig. 134.—A Diagram showing how to connect two Simple Telegraph Stations.Fig. 134.—A Diagram showing how to connect two Simple Telegraph Stations.The key and sounder should be placed in series with one or two cells of a battery. Pressing the key will then cause the armature of the sounder to be drawn down and make a click. When the key is released, the armature will be drawn up by the spring or rubber band and make a second click.Hardly a boy interested in mechanics and electricity has not at some time or other wished for a telegraph instrument with which to put up a "line" with his chum.A practical working set of such instruments can be very easily constructed, and with little expense, by following the sketches and instructions given here.The magnets for the sounder may either be constructed by the intending telegraph operator or secured from some old electrical instrument such as a magneto-bell. In the latter case, the hardest part of the work will be avoided.If they are to be home-made, the following suggestions may prove of value in carrying out their construction.Fig. 135.—A Complete Telegraph Set, consisting of a Keyboard and a Sounder.Fig. 135.—A Complete Telegraph Set, consisting of a Keyboard and a Sounder.The cores are made from one-quarter-inch stove-bolts with the heads cut off. The magnet heads are cut out of hard-wood fiber, one-eighth of an inch thick and one inch in diameter. They should fit tightly and be held in place with glue. They are separated so as to form a winding space between of seven-eighths of an inch. The magnets should be wound full of No. 25 B. & S. gauge cotton-covered wire.Fig. 136.—Details of the Telegraph Set shown in Figure 135.Fig. 136.—Details of the Telegraph Set shown in Figure 135.The yoke is made of enough strips of sheet-iron, one-half inch wide and two inches long, to form a pile one-quarter of an inch thick. Two one-quarter-inch holes are bored in the opposite ends of the yoke, one and one-half inches apart. The lower ends of the magnet cores are passed through these holes. The ends should project one-half of an inch beyond the yoke.They are passed through two holes in a base-board three-quarters of an inch thick. The holes are countersunk from the lower side, so that a nut can be screwed on the lower end of each and the magnets held tightly in an upright position. The remaining parts of the instrument are very easily made, and are so clearly shown by the drawing that it is hardly necessary to say more than a few words in explanation.The lever or tongue, the anvil, the standard, and the lever of the key are all cut out of hard-wood according to the pattern shown in the illustration.The armature is a piece of soft iron fastened to the lever with a small brass screw.Tacks are placed under the heads of the adjusting screws on the sounder so that it will click more loudly.The rubber band acts as a spring to counteract the weight of the armature and lever and draw it up as soon as the current is cut off. The movement of the lever should be so adjusted that it is only sufficient to make an audible click.Use care to avoid friction between the lever and the standard, so that the former will move with perfect freedom.All the screws used in the work should be round-headed brass wood screws with the points filed flat. Bore a small hole before screwing them into place so as to avoid splitting the wood.The construction of the key is even more simple than that of the sounder. It should move up and down without any side motion.The circuit-closer should be kept closed when the instruments are not in use, and when you are receiving a message. As soon as you are through receiving and wish to transmit, you should open your circuit-closer and your friend close his.The tension of the spring under the lever of the key must be adjusted to suit the needs of each individual operator.Fig. 137.—A Diagram showing how to connect two Complete Telegraph Sets, using one Line Wire and a Ground.Fig. 137.—A Diagram showing how to connect two Complete Telegraph Sets, using one Line Wire and a Ground. The Two-Point Switches throw the Batteries out of Circuit when the Line is not in use.The diagram for connecting the instruments is self-explanatory. In cities or towns where a "ground" is available by connecting to the gas or water pipes, one line wire may be easily dispensed with. Or, if desirable, a ground may be formed by burying a large plate of zinc (three or four feet square) in a moist spot and leading the wire to it.
The little telegraph instruments shown in Figures 132 and 133 are not practical for long lines but may be used for ticking messages from one room to another, and can be made the source of much instruction and pleasure.
Fig. 132.—A Simple Home-made Telegraph Key.Fig. 132.—A Simple Home-made Telegraph Key.
Fig. 132.—A Simple Home-made Telegraph Key.
The key is a strip of brass fastened to a wooden base in the manner shown in Figure 132. It is fitted with a knob of some sort on the front end, so that it is conveniently gripped with the fingers.
The little bridge is made from heavy sheet-brass and prevents the lever from moving too far away from the contact on the upward stroke.
Connections are made to the key lever at the back end and the contact in front by the binding-posts,AandB. The post,C, connects with the bridge.
The sounder consists of two small electromagnets mounted in a vertical position on a wooden base. The magnets are connected at the bottom by a strip of heavy sheet-iron which acts as a yoke.
Fig. 133.—A Simple Home-made Telegraph Sounder.Fig. 133.—A Simple Home-made Telegraph Sounder.
Fig. 133.—A Simple Home-made Telegraph Sounder.
The armature is made out of sheet-iron, rolled up in the manner shown in the illustration. One end of the armature is fastened to a wooden block in such a position that the armature comes directly over the magnets and about one-eighth of an inch above them. The opposite end of the armature moves up and down for about an eighth of an inch between two screws, each fastened in a wooden block mounted on an upright board in the back of the magnets. The purpose of the screws is to make the "click" of the sounder louder and clearer than it would be if the armature only struck the wood.
A rubber band or a small wire spring passing over a screw and connected at the other end to the armature will draw the latter away from the magnets when the current is not passing.
The terminals of the magnets are connected to binding-posts mounted on the base.
Fig. 134.—A Diagram showing how to connect two Simple Telegraph Stations.Fig. 134.—A Diagram showing how to connect two Simple Telegraph Stations.
Fig. 134.—A Diagram showing how to connect two Simple Telegraph Stations.
The key and sounder should be placed in series with one or two cells of a battery. Pressing the key will then cause the armature of the sounder to be drawn down and make a click. When the key is released, the armature will be drawn up by the spring or rubber band and make a second click.
Hardly a boy interested in mechanics and electricity has not at some time or other wished for a telegraph instrument with which to put up a "line" with his chum.
A practical working set of such instruments can be very easily constructed, and with little expense, by following the sketches and instructions given here.
The magnets for the sounder may either be constructed by the intending telegraph operator or secured from some old electrical instrument such as a magneto-bell. In the latter case, the hardest part of the work will be avoided.
If they are to be home-made, the following suggestions may prove of value in carrying out their construction.
Fig. 135.—A Complete Telegraph Set, consisting of a Keyboard and a Sounder.Fig. 135.—A Complete Telegraph Set, consisting of a Keyboard and a Sounder.
Fig. 135.—A Complete Telegraph Set, consisting of a Keyboard and a Sounder.
The cores are made from one-quarter-inch stove-bolts with the heads cut off. The magnet heads are cut out of hard-wood fiber, one-eighth of an inch thick and one inch in diameter. They should fit tightly and be held in place with glue. They are separated so as to form a winding space between of seven-eighths of an inch. The magnets should be wound full of No. 25 B. & S. gauge cotton-covered wire.
Fig. 136.—Details of the Telegraph Set shown in Figure 135.Fig. 136.—Details of the Telegraph Set shown in Figure 135.
Fig. 136.—Details of the Telegraph Set shown in Figure 135.
The yoke is made of enough strips of sheet-iron, one-half inch wide and two inches long, to form a pile one-quarter of an inch thick. Two one-quarter-inch holes are bored in the opposite ends of the yoke, one and one-half inches apart. The lower ends of the magnet cores are passed through these holes. The ends should project one-half of an inch beyond the yoke.
They are passed through two holes in a base-board three-quarters of an inch thick. The holes are countersunk from the lower side, so that a nut can be screwed on the lower end of each and the magnets held tightly in an upright position. The remaining parts of the instrument are very easily made, and are so clearly shown by the drawing that it is hardly necessary to say more than a few words in explanation.
The lever or tongue, the anvil, the standard, and the lever of the key are all cut out of hard-wood according to the pattern shown in the illustration.
The armature is a piece of soft iron fastened to the lever with a small brass screw.
Tacks are placed under the heads of the adjusting screws on the sounder so that it will click more loudly.
The rubber band acts as a spring to counteract the weight of the armature and lever and draw it up as soon as the current is cut off. The movement of the lever should be so adjusted that it is only sufficient to make an audible click.
Use care to avoid friction between the lever and the standard, so that the former will move with perfect freedom.
All the screws used in the work should be round-headed brass wood screws with the points filed flat. Bore a small hole before screwing them into place so as to avoid splitting the wood.
The construction of the key is even more simple than that of the sounder. It should move up and down without any side motion.
The circuit-closer should be kept closed when the instruments are not in use, and when you are receiving a message. As soon as you are through receiving and wish to transmit, you should open your circuit-closer and your friend close his.
The tension of the spring under the lever of the key must be adjusted to suit the needs of each individual operator.
Fig. 137.—A Diagram showing how to connect two Complete Telegraph Sets, using one Line Wire and a Ground.Fig. 137.—A Diagram showing how to connect two Complete Telegraph Sets, using one Line Wire and a Ground. The Two-Point Switches throw the Batteries out of Circuit when the Line is not in use.
Fig. 137.—A Diagram showing how to connect two Complete Telegraph Sets, using one Line Wire and a Ground. The Two-Point Switches throw the Batteries out of Circuit when the Line is not in use.
The diagram for connecting the instruments is self-explanatory. In cities or towns where a "ground" is available by connecting to the gas or water pipes, one line wire may be easily dispensed with. Or, if desirable, a ground may be formed by burying a large plate of zinc (three or four feet square) in a moist spot and leading the wire to it.
How To Build a Telegraph RelayIn working a telegraph over a long line or where there are a large number of instruments on one circuit, the currents are often not strong enough to work the sounder directly. In such a case arelayis used. The relay is built on the same principle as a sounder, but the parts are made much lighter, so that the instrument is more sensitive. The armature of a relay is so small and its movement so little that its clicking is scarcely audible. It is therefore fitted with a second set of contacts and connected to a battery and a sounder, which is to set in operation every time the contacts close. The principle of a relay is that a weak current of insufficient strength to do the work itself may set a strong local current to do its work for it.There are many forms of relays, and while that which is described below is not of the type commonly used on telegraph lines, it has the advantage of being far more sensitive than any instrument of the regular line relay type that the average experimenter could build.Fig. 138.—Details of the Relay Parts.Fig. 138.—Details of the Relay Parts.Make the magnets from one-quarter-inch stove-bolts, and cut them off so that they will form a core about two and one-quarter inches long. Fit each of the cores with two fiber heads to hold the wire in place. Insulate the legs with paper and wind each with about fifty layers of No. 30 B. & S. gauge single-cotton-covered magnet wire. The winding space between the magnet’s heads should be one and one-eighth inches.The upper ends of the magnet cores should be allowed to project about one-quarter of an inch beyond the fiber head. The end of the core is filed flat, as shown in the illustration.The magnets are mounted upon an iron yoke, three-sixteenths of an inch thick. The holes in the yoke should be spaced so that there is a distance of one and one-half inches between the centers of the magnet cores.The armature of the relay is mounted on a small steel shaft with sharp points at each end. The exact shape of the armature may be best understood from the illustrations.The lower end of the shaft rests in a small cone-shaped depression made by driving a center punch into the yoke half-way between the two magnets.The top bearing is a strip of brass projecting from a wooden support. The end of the shaft rests in a depression similar to that in the yoke.The contact lever is made of brass and forced on the shaft below the armature. It swings between a small brass clip fastened to one side of the support and a little screw held in a similar clip on the opposite side.The contact clip is made of spring brass about No. 22 gauge in thickness. It may be adjusted by a screw passing through the support.The armature may be controlled in its movement so that the latter will be very slight by adjusting the screws.There should not be any friction in the bearings and the armature should move with perfect freedom. The armature should approach the ends of the magnet cores until a space about the thickness of heavy paper separates them and should not touch them.Fig. 139.—The Completed Relay.Fig. 139.—The Completed Relay.The spring is made of fine brass wire. It is fastened to the armature shaft, and the screw mounted on the wooden support with a piece of silk thread. The thread is passed around the shaft once or twice so that the tension of the spring will cause the armature to move away from the pole pieces just as soon as the current flowing through the magnets ceases.Fig. 140.—A Diagram showing how to connect a Relay, Sounder, and Key.Fig. 140.—A Diagram showing how to connect a Relay, Sounder, and Key. Closing the Key will operate the Relay. The Relay will then operate the Sounder in turn.The tension of the spring may be adjusted by turning the screw with a screw-driver. If the armature tends to stick to the magnet poles fasten a small piece of paper to the poles with some shellac.The terminals of the magnets are connected to two binding-posts markedAandB. The binding-posts markedCandDare connected respectively to the contact clip and the brass bearing on the top of the wooden support.The diagram in Figure 140 shows how the relay is connected to a telegraph line.
In working a telegraph over a long line or where there are a large number of instruments on one circuit, the currents are often not strong enough to work the sounder directly. In such a case arelayis used. The relay is built on the same principle as a sounder, but the parts are made much lighter, so that the instrument is more sensitive. The armature of a relay is so small and its movement so little that its clicking is scarcely audible. It is therefore fitted with a second set of contacts and connected to a battery and a sounder, which is to set in operation every time the contacts close. The principle of a relay is that a weak current of insufficient strength to do the work itself may set a strong local current to do its work for it.
There are many forms of relays, and while that which is described below is not of the type commonly used on telegraph lines, it has the advantage of being far more sensitive than any instrument of the regular line relay type that the average experimenter could build.
Fig. 138.—Details of the Relay Parts.Fig. 138.—Details of the Relay Parts.
Fig. 138.—Details of the Relay Parts.
Make the magnets from one-quarter-inch stove-bolts, and cut them off so that they will form a core about two and one-quarter inches long. Fit each of the cores with two fiber heads to hold the wire in place. Insulate the legs with paper and wind each with about fifty layers of No. 30 B. & S. gauge single-cotton-covered magnet wire. The winding space between the magnet’s heads should be one and one-eighth inches.
The upper ends of the magnet cores should be allowed to project about one-quarter of an inch beyond the fiber head. The end of the core is filed flat, as shown in the illustration.
The magnets are mounted upon an iron yoke, three-sixteenths of an inch thick. The holes in the yoke should be spaced so that there is a distance of one and one-half inches between the centers of the magnet cores.
The armature of the relay is mounted on a small steel shaft with sharp points at each end. The exact shape of the armature may be best understood from the illustrations.
The lower end of the shaft rests in a small cone-shaped depression made by driving a center punch into the yoke half-way between the two magnets.
The top bearing is a strip of brass projecting from a wooden support. The end of the shaft rests in a depression similar to that in the yoke.
The contact lever is made of brass and forced on the shaft below the armature. It swings between a small brass clip fastened to one side of the support and a little screw held in a similar clip on the opposite side.
The contact clip is made of spring brass about No. 22 gauge in thickness. It may be adjusted by a screw passing through the support.
The armature may be controlled in its movement so that the latter will be very slight by adjusting the screws.
There should not be any friction in the bearings and the armature should move with perfect freedom. The armature should approach the ends of the magnet cores until a space about the thickness of heavy paper separates them and should not touch them.
Fig. 139.—The Completed Relay.Fig. 139.—The Completed Relay.
Fig. 139.—The Completed Relay.
The spring is made of fine brass wire. It is fastened to the armature shaft, and the screw mounted on the wooden support with a piece of silk thread. The thread is passed around the shaft once or twice so that the tension of the spring will cause the armature to move away from the pole pieces just as soon as the current flowing through the magnets ceases.
Fig. 140.—A Diagram showing how to connect a Relay, Sounder, and Key.Fig. 140.—A Diagram showing how to connect a Relay, Sounder, and Key. Closing the Key will operate the Relay. The Relay will then operate the Sounder in turn.
Fig. 140.—A Diagram showing how to connect a Relay, Sounder, and Key. Closing the Key will operate the Relay. The Relay will then operate the Sounder in turn.
The tension of the spring may be adjusted by turning the screw with a screw-driver. If the armature tends to stick to the magnet poles fasten a small piece of paper to the poles with some shellac.
The terminals of the magnets are connected to two binding-posts markedAandB. The binding-posts markedCandDare connected respectively to the contact clip and the brass bearing on the top of the wooden support.
The diagram in Figure 140 shows how the relay is connected to a telegraph line.
How To Learn To TelegraphThe instruments so far described have been practical working telegraph instruments, but they lack the fine points of commercial apparatus and it is not possible to become as efficient an operator with their aid as with a real key and sounder.If the young experimenter desires to become a proficient telegraph operator, the first thing to do is to purchase a Learner’s telegraph key and sounder.Connect a dry cell to the binding-posts on the back of the instrument. Screw the set down on a table about eighteen inches from the front edge, so that there is plenty of room for the arm to rest. See that none of the various adjustment screws about the instrument are loose and that the armature of the sounder moves freely up and down through a distance of about one-sixteenth of an inch.The spring which draws the lever upwards away from the magnets should be set only at sufficient tension to raise the lever when no current is passing. If too tight, the spring will not allow the armature to respond to the current flowing through the magnets.The key is provided with several adjustment-screws to regulate the tension and the play of the lever to suit the hand of the operator. A little practice will enable the student to judge best for himself just how the key should be set.The next step is to memorize the alphabet, so that each character can instantly be called to mind at will. The punctuation marks are not used very frequently, and the period is the only one which the student need learn at first.The Morse alphabet consists of dots, dashes, and spaces. Combinations of these signals spell letters and words.Many of the characters are the reverse of others. For example,Ais the reverse ofN.BandF,DandU,CandR,QandX,Zand&, are the other reverse letters, so if the formation of one of each of these letters is memorized the reverse is easily mastered.It is important that the beginner should learn how properly to grasp the key, for habits are easily formed and a poor position will limit the sending speed of the operator.Place the first or index finger on the top of the key-handle, with the thumb under the edge; and the second finger on the opposite side. The fingers should be curved so as to form a quarter-section of a circle. Bring the third and fourth fingers down so that they are almost closed on the palm of the hand. Rest the arm on the table in front of the key and allow the wrist to be perfectly limber.Fig. 141.—How to hold a Telegraph Key.Fig. 141.—How to hold a Telegraph Key.The grasp on the key should be firm but not rigid. Avoid using too much strength or a light hesitating touch. Endeavor to acquire a positive, firm up and down motion of the key. Avoid all side pressure, and do not allow the fingers to leave the key when making the signals. The movement is made principally with the wrist, with the fingers and hand perfectly elastic.A dot is made by a single instantaneous, downward stroke of the key. A dash is made by holding the key down for the same period of time that it takes to make three dots. A long dash is made by holding the key down for the same time that it takes to make five dots.A space in the letters, such as, for instance, the space between the first and last two dots in the letterRshould occupy the time of one dot. The space between each letter should occupy the time required for two dots, and the space between words should occupy the time required for three dots.Commence the use of the key by making dots in succession, first at the rate of two every second, and increasing the speed until ten can be made. Practice should be continued until three hundred and sixty dots a minute can be made with perfect regularity.Then begin making dashes at the rate of two every three seconds, and continue until one hundred and twenty a minute can be made with perfect regularity.Practise the long dashes at the rate of one a second, and increase until ninety can be made in a minute.Fig. 142.—The Morse Telegraphic Code.Fig. 142.—The Morse Telegraphic Code.When this has been accomplished, practise the following letters until they can be perfectly made. Each row of letters is an exercise which should be practised separately until mastered.Dot LettersE I S H P 6Dot and Space LettersO C R Y Z &Dash LettersT L M 5 ODots and DashesA U V 4Dashes and DotsN D B 8Mixed Dots and DashesF G J K Q W X 1 2 3 7 9 PeriodAfter you can write these different letters, practise making words. Select a list of commonly used words. When words seem easy to write, practise sending pages from a book.Systematic and continual practice will enable the student to make surprising progress in mastering the art of sending.Reading and receiving messages must be practised with a companion student. Place two instruments in separate rooms or in separate houses so that the operators will be entirely dependent upon the instruments for their communication with each other. Start by transmitting and receiving simple messages. Then use pages from a book, and increase the speed until it is possible to send and receive at least 15 words a minute without watching the sounder but merely depending upon the clicks to determine the duration of the dots and dashes.Figure 140 shows how to arrange a regular telegraph line for two stations. Gravity batteries should be used for regular telegraph work. It is necessary that the key should be kept closed by having its circuit-closer shut when messages are not being sent. If one of the keys is left open the circuit is broken, and it is not possible for a person at the other end of the line to send a message.Every telegraph office has a name or call usually consisting of two letters; thus for New York the call might be N. Y. and for Chicago, C. H.If New York should desire to call Chicago, he would repeat the call letters, C H., until answered. Chicago would answer by sending I, several times and signing, C H. When so answered, New York would proceed with the message.MICROPHONES AND TELEPHONES
The instruments so far described have been practical working telegraph instruments, but they lack the fine points of commercial apparatus and it is not possible to become as efficient an operator with their aid as with a real key and sounder.
If the young experimenter desires to become a proficient telegraph operator, the first thing to do is to purchase a Learner’s telegraph key and sounder.
Connect a dry cell to the binding-posts on the back of the instrument. Screw the set down on a table about eighteen inches from the front edge, so that there is plenty of room for the arm to rest. See that none of the various adjustment screws about the instrument are loose and that the armature of the sounder moves freely up and down through a distance of about one-sixteenth of an inch.
The spring which draws the lever upwards away from the magnets should be set only at sufficient tension to raise the lever when no current is passing. If too tight, the spring will not allow the armature to respond to the current flowing through the magnets.
The key is provided with several adjustment-screws to regulate the tension and the play of the lever to suit the hand of the operator. A little practice will enable the student to judge best for himself just how the key should be set.
The next step is to memorize the alphabet, so that each character can instantly be called to mind at will. The punctuation marks are not used very frequently, and the period is the only one which the student need learn at first.
The Morse alphabet consists of dots, dashes, and spaces. Combinations of these signals spell letters and words.
Many of the characters are the reverse of others. For example,Ais the reverse ofN.BandF,DandU,CandR,QandX,Zand&, are the other reverse letters, so if the formation of one of each of these letters is memorized the reverse is easily mastered.
It is important that the beginner should learn how properly to grasp the key, for habits are easily formed and a poor position will limit the sending speed of the operator.
Place the first or index finger on the top of the key-handle, with the thumb under the edge; and the second finger on the opposite side. The fingers should be curved so as to form a quarter-section of a circle. Bring the third and fourth fingers down so that they are almost closed on the palm of the hand. Rest the arm on the table in front of the key and allow the wrist to be perfectly limber.
Fig. 141.—How to hold a Telegraph Key.Fig. 141.—How to hold a Telegraph Key.
Fig. 141.—How to hold a Telegraph Key.
The grasp on the key should be firm but not rigid. Avoid using too much strength or a light hesitating touch. Endeavor to acquire a positive, firm up and down motion of the key. Avoid all side pressure, and do not allow the fingers to leave the key when making the signals. The movement is made principally with the wrist, with the fingers and hand perfectly elastic.
A dot is made by a single instantaneous, downward stroke of the key. A dash is made by holding the key down for the same period of time that it takes to make three dots. A long dash is made by holding the key down for the same time that it takes to make five dots.
A space in the letters, such as, for instance, the space between the first and last two dots in the letterRshould occupy the time of one dot. The space between each letter should occupy the time required for two dots, and the space between words should occupy the time required for three dots.
Commence the use of the key by making dots in succession, first at the rate of two every second, and increasing the speed until ten can be made. Practice should be continued until three hundred and sixty dots a minute can be made with perfect regularity.
Then begin making dashes at the rate of two every three seconds, and continue until one hundred and twenty a minute can be made with perfect regularity.
Practise the long dashes at the rate of one a second, and increase until ninety can be made in a minute.
Fig. 142.—The Morse Telegraphic Code.Fig. 142.—The Morse Telegraphic Code.
Fig. 142.—The Morse Telegraphic Code.
When this has been accomplished, practise the following letters until they can be perfectly made. Each row of letters is an exercise which should be practised separately until mastered.
Dot Letters
Dot Letters
E I S H P 6
E I S H P 6
E I S H P 6
Dot and Space Letters
Dot and Space Letters
O C R Y Z &
O C R Y Z &
O C R Y Z &
Dash Letters
Dash Letters
T L M 5 O
T L M 5 O
T L M 5 O
Dots and Dashes
Dots and Dashes
A U V 4
A U V 4
A U V 4
Dashes and Dots
Dashes and Dots
N D B 8
N D B 8
N D B 8
Mixed Dots and Dashes
Mixed Dots and Dashes
F G J K Q W X 1 2 3 7 9 Period
F G J K Q W X 1 2 3 7 9 Period
F G J K Q W X 1 2 3 7 9 Period
After you can write these different letters, practise making words. Select a list of commonly used words. When words seem easy to write, practise sending pages from a book.
Systematic and continual practice will enable the student to make surprising progress in mastering the art of sending.
Reading and receiving messages must be practised with a companion student. Place two instruments in separate rooms or in separate houses so that the operators will be entirely dependent upon the instruments for their communication with each other. Start by transmitting and receiving simple messages. Then use pages from a book, and increase the speed until it is possible to send and receive at least 15 words a minute without watching the sounder but merely depending upon the clicks to determine the duration of the dots and dashes.
Figure 140 shows how to arrange a regular telegraph line for two stations. Gravity batteries should be used for regular telegraph work. It is necessary that the key should be kept closed by having its circuit-closer shut when messages are not being sent. If one of the keys is left open the circuit is broken, and it is not possible for a person at the other end of the line to send a message.
Every telegraph office has a name or call usually consisting of two letters; thus for New York the call might be N. Y. and for Chicago, C. H.
If New York should desire to call Chicago, he would repeat the call letters, C H., until answered. Chicago would answer by sending I, several times and signing, C H. When so answered, New York would proceed with the message.
MICROPHONES AND TELEPHONES