When using the accumulators they should never be fully discharged.
The Charging Circuit.—The diagram (Fig. [66]) shows how a charging circuit is formed. The lamps are connected up in parallel, as illustrated. Each 16-candle-power 105-volt lamp will carry ½ ampere, so that, supposing we have a dynamo which gives 110 volts, and we want to charge a 4-volt accumulator, there will be 5-volt surplus to go to the accumulator. If, for instance, you want the cell to have a charge of 2 amperes, four of these lamps should be connected up in parallel. If 3 amperes are required, use 6 lamps, and so on.
CHAPTER IX[ToC]
THE TELEGRAPH
The telegraph is a very simple instrument. The key is nothing more or less than a switch which turns the current on and off alternately.
The signals sent over the wires are simply the audible sounds made by the armature, as it moves to and from the magnets.
Mechanism in Telegraph Circuits.—A telegraph circuit requires three pieces of mechanism at each station, namely, a key used by the sender, a sounder for the receiver, and a battery.
The Sending Key.—The base of the sending instrument is six inches long, four inches wide, and three-quarters of an inch thick, made of wood, or any suitable non-conducting material. The key (A) is a piece of brass three-eighths by one-half inch in thickness and six inches long. Midway between its ends is a cross hole, to receive the pivot pin (B), which also passes through a pair of metal brackets (C, D), the bracket C having a screw to hold one of the line wires, and the other bracket having a metal switch (E) hinged thereto. This switch bar, like the brackets, is made of[p. 91] brass, one-half inch wide by one-sixteenth of an inch thick.