Found in a Raytheon transistor manual from the 1950s, this circuit uses one of the first commercially available transistors, the CK722. The circuit is for using a small speaker as a microphone.
We found this multiple thermostat circuit in July 1980 Radio Electronics magazine. It uses...
This circuit is from a 1986 Revista Española de Electrónica. It consists of an amplifier with...
Suggested by a 1968 Philips documentation this Eccles Jordan rocker as it was called can operate...