The output of this audion was a radio-frequency current modulated by the voice.
Suppose we transmit at a radio-frequency of 50,000 cycles and modulate that with speech.
In that of Fig. 95 it is the radio-frequency effect which is amplified.
If the voice is high pitched there are more rapid variations in the strength of the radio-frequency current.
This coil has a small inductance but it is enough to offer a large impedance to radio-frequency currents.
If the radio-frequency is 500,000 cycles we need a still smaller range of wave-lengths to transmit the necessary side-bands.
Heaters to destroy immediate vegetation, and Radio-Frequency beams to kill insects and their larvae over a wider area.