We found this circuit in a 1976 documentation. The FET can be BF245 or MPF102 and the power supply need not be symmetrical. The FET in the feedback acts as an automatic gain control.
This light-controlled circuit uses a 6 V or 12 V relay depending on the supply. The transistor can be the...
This circuit was found in an American publication from 1965. The circuit uses components from that...
This powerful inverter provides a high-quality sine wave signal. I found it in a Radio Electronics issue...