The higher voltage necessary to operate an audion is supplied by a battery consisting of fifteen flashlight batteries, each flashlight battery being composed of three separate cells. The batteries are connected to an eight-point switch so that throwing the switch on the first point will connect five sets of batteries. The second point places five more in circuit and each additional point one set only. It is also a good plan to connect a four-point switch and three separate cells of battery in series with the eight-point switch so that they may be added to the circuit one at a time and the potential varied more closely than the steps on the eight-point switch permit. The maximum voltage of such a battery is approximately 56 volts.
The diagram in Fig. 166 shows exactly how an audion is connected. The wires A and B are the terminals leading to the tuning coil or loose coupler. It is not necessary that the telephone receivers used with an audion be wound to a high resistance in order to secure good results.
Fig. 166. Audion Circuit.
The audion is placed in operation by turning the rheostat until the filament lights brightly. Then adjust the voltage of the high potential battery until the signals are clearest. If the voltage is too high the audion will become filled with a bluish light and the voltage should be immediately reduced. The signals will be loudest when the filament is brilliantly lighted. No more current should be passed through the filament than is necessary to render the signals plain, for if "forced" its life will be limited to only a few hours.
Fig. 167. Rotary Variable Condenser.
APPENDIX.
[PUBLIC No. 264.]
[S. 6412.]