This circuit was found in the December 1992 issue of Radio Electronics magazine. The current is a few mA and the maximum input voltage is around 12 V.
This simple transmitter can send signals to distances up to 200 m, depending on the power supply...
In the figure we have the original version of an amplifier with high input impedance, 1.2 M ohms....
This circuit powered by photovoltaic cells was found in the November 1998 issue of Electronics Now magazine....