FIG. 11.—BOAT TELEPHONE, MODEL 1906.
FIG. 11.—BOAT TELEPHONE, MODEL 1906.
Lag screws are also provided, by means of which the ends of the frames can be fastened to the deck of the vessel if desired.
The reel axle is 2½ by 2½ inch squared iron, rounded at the ends for 6 inches to fit the journals of the frame. A disk secured by a set-screw at one end of the axle and the friction brake wheel at the other end hold the axle in position with respect to the reel.
The brake wheel is 18 inches in diameter. The friction band is 1½ inches by ⅛ inch, and is fastened at one end to one of the standards of the frame. The other end is attached to a lever whose fulcrum is also attached to the same standard.
Boat telephones.—The different models in use are as follows:
(a)Model 1904.—The system consists of two telephone hand sets, a buzzer, and a battery of dry cells of about 8 volts, all connected in series by means of cable and earth connections.
In operating the telephones a call is made by pressing the button, and when talking the lever is held down.
(b)Model 1906.—The system consists of two telephone hand sets, a reactance coil, and a source of energy that will furnish about 15 volts, dry cells preferred, connected as shown infigure 11. The terminals do not have to be poled, as the receiver is not in the primary circuit and can not be demagnetized.
To regulate the buzzer, remove the cap in the base and with a small screw driver loosen the lock nut on the center screw (a small portion of a turn is all that is necessary). With a smaller screw driver the screw may be adjusted to increase or decrease the rate of vibration, increasing or decreasing the sound. Then tighten the lock nut. In case the contact is dirty the entire buzzer and condenser may be removed bydisconnecting the cord and removing the screw on the back of the telephone just below the call button. As the contacts are aluminum, this will seldom have to be done.
(c)Model 1909.—The system consists of two telephone hand sets, an apparatus box, and a battery of from 7 to 10 volts, all connected as shown infigure 12. The talking and ringing circuits are normally open at the talking and ringing buttons, respectively.
Apparatus box.—Seven dry cells in series should be connected to the posts of the apparatus box marked “+” and “-,” and the post marked “G” connected to a ground plate.
Shore hand set.—The blue cord of the shore hand set should be connected to the ground plate. Either of the red cords of the shore hand set should be connected to the post in the apparatus box marked “L” and the other to the conductor in the cable that is to be used for telephoning purposes.
Boat hand set.—The blue cord of the boat hand set should be connected to the ground plate and one of the red cords to the conductor in the cable to which the hand set on the shore is connected. The other red cord is free.
Signaling.—Fromfigure 12it will be seen that in either hand set, when neither the ringing nor the talking switch is closed, a condenser within the hand set is in series with the transmitter and the receiver, so that the practical effect is to permit an alternating or variable current to pass through the transmitter and the receiver, but to prevent a direct or continuous current from so doing.
By pressing the ringing key of either hand set the circuit in that hand set is closed through the 1,000 ohms resistance and the receiver to ground. Thus, when the ringing key of the boat hand set is pressed, this allows the direct current from the battery to pass (see fig. 12) through f, e, d, c, “B,” b, a, line, the ringing key, 1,000-ohm resistance, and receiver of the boat hand set, to ground, and back through o and p to battery. Similarly, a circuit through the battery, f, “A,” and a, is made, thus placing relays “A” and “B” in parallel. The relay “B” operates, but relay “A,” being less sensitive than “B,” does not operate. Relay “B” closes the circuit at l, and thus completes the circuit from battery through f, e, d, c, k, l, “C,” o, p, back to battery. This causes relay “C” to operate and to complete a local circuit from battery through f, e, d, k, m, s, primary, t, vibrator, p, back to battery, causing the vibrator to vibrate and inducing in the secondary winding of the induction coil an alternating current, which passes through the 1 M. F. and 2 M. F. condensers, through the hand sets in parallel, and by alternately increasing and decreasing the attraction of the receiver magnets for their diaphragms produces a loud humming sound in each receiver.
Similarly the shore station may call the boat station.
FIG. 12.—BOAT TELEPHONE, MODEL 1909.
FIG. 12.—BOAT TELEPHONE, MODEL 1909.
Talking.—When the ringing key is released and the talking key is depressed the 1,000-ohm resistance is cut out and the condenser in the hand set is short circuited. The current is then sufficient to operate relay “A,” and this relay in operating allows the other relays to resume their normal positions.
When the variations in the pressure upon the transmitter diaphragm in either hand set varies the resistance of the corresponding branch circuit a slight variation in the current from the battery is produced. The internal resistance of the battery is sufficient to produce a slight variation in its terminal voltage. The resulting variations in the line voltage, and hence in the drop across the receivers, produce the usual vibrations in the receiver diaphragms. These variations also produce slight variations in the current through the primary winding of the induction coil, resulting in greater variations across the terminals of the secondary winding. Since the secondary winding is in series with the battery, the practical effect is to amplify the variations in the line voltage, and hence in the talking currents.
Successful working of the relays is obtained only by a careful adjustment of the screws which regulate the throw of the armatures. The relay “A” is located in front of the “+” battery post, the relay “C” in front of the “G” post.
In addition to the above matériel there are necessary for the mine system certain electrical instruments, as well as tools, appliances, and supplies requiring no special description, which are enumerated in the supply list. (Appendix 8.)
Figures17aand17b, at the end of the book, show the construction of an improvised mine target.