Found in the July 1970 Radio Electronics magazine, this circuit has an adjustable activation time that depends on capacitor C1. The SCR may be a 106 series equivalent.
The integrated circuit used is a voltage reference from Motorola. This configuration was obtained in...
This circuit is from a Radio Electronics from October 1970. The circuit uses transistors from that...
This circuit was obtained from a 1977 magazine, but can still be mounted using BC548 for TR1 and...