This circuit was found in the 1969 RCA thyristor manual. The circuit has a limiter (clipping) with two 12 V zener diodes in opposition to cut power grid pulses that may influence the trigger.
Using bipolar, FETs and unijunction this long-lasting timer can reach 10 hours with good quality...
This 1-transistor circuit for currents up to 50 mA was found in the August 1974 Radio Electronics...
We found this circuit in a 1969 General Electric documentation. The circuit uses transistors of the...