This small transmitter appeared in the March 1989 issue of Radio Electronics magazine. The two-transistor circuit used an electret microphone and had a range of a few dozen meters.
This circuit is of great use today, when solar energy is becoming increasingly important. The...
This circuit is from an American publication of 1978. It can be assembled with modern transistors, since...
This high-sensitivity circuit was found in a 1980s documentation. The source can be a 9 V battery...