The purpose of this circuit is to cut off the high voltage when the bias voltage fails. The circuit is from a 1975 documentation and can be adapted for other purposes.
We found this circuit in the October 1978 issue of Radio Electronics magazine. The magazine...
This siren configuration using the 555 has already been explored in other circuits on this site. In...
VR can be from 50 to 220k it is recommended to connect a 100-ohm resistor in series. The lamp may...