The device used a tickler-feedback Armstrong oscillator circuit. The Audion is mounted outside, on the side of the enclosure, so the operator can check if the filament is glowing and adjust the filament voltage visually. Audions were always mounted hanging upside down, so the fragile filament in the tube wouldn't sag and touch the grid. The telephone-type carbon microphone was connected directly in the transmitter's antenna wire, and its varying resistance modulated the current going to the antenna. The low power of the early Audion gave it a limited range of 1 to 3 miles.

The text of the article that accompanied the photo:
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.