In use telephone indicator (CB8665E)

This circuit was found in a 90s Electronics Now. The circuit can use a TIC106 for the SCR.

Dual trace for oscilloscope (CB5438E)
This circuit shows on the screen of an oscilloscope two signals alternately at a frequency that depends...
Signal Relay (CB5940E)
This audio signal relay was found in an American 1980s documentation. The relay is in accordance...
High gain photo relay (CB8268E)
This circuit was found in Ferranti's 1967 documentation. The circuit drives a 40 V relay, but it can...