This 1969 Mullar circuit appears elsewhere on this site. The circuit uses germanium diodes and the indicator is microammeter with zero in the center of the scale.
Suggested by an American documentation for 1969 neon lamps, this circuit provides SCR control with...
This circuit was obtained in a 1976 amateur radio manual. The circuit can be made with a 2N2222...
This circuit was taken from the 1974 Ferranti transistor manual. It is intended to use a common...