We found this circuit in the September 1992 issue of Radio Electronics magazine. It can be triggered by any signal above ½ Vcc, where Vcc is the supply voltage.
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...