This circuit was found in a 1967 US documentation. The FET is general purpose and the 6V zener. The circuit has a very fast switching action.
This circuit was found in Motorola documentation from 1966. The lamps are according to power and...
This circuit, which uses components still common today, was found in a 1997 documentation. It...
This circuit is intended to apply the music signal from a stereo to a telephone line for the...