Apparatus for generating in an incandescent lamp from direct-current energy continuous high-frequency oscillations to be used for wireless telephony and telegraphy, as well as for numerous laboratory applications, is being made by the Radio Telephone & Telegraph Company, 309 Broadway, New York. This equipment is called an oscillating "audion" transmitter and can be connected to either a 110-volt or a 250-volt lighting circuit. By means of the small 3.5-volt amplifier bulb used with this apparatus direct current can be transformed to alternating current at frequencies of from sixty cycles per second to 1,000,000 cycles per second. With this form of transmitter it is possible to telephone one to three miles, and the device is well adapted for use on small yachts, tugs, ferryboats, etc.
When a storage-battery supply is available this oscillating transmitter can serve as a receiver also, both the functions of transmitting and receiving being performed by means of the same bulb with the aid of a telephone receiver connected to the wing-filament circuit.