This CMOS circuit was obtained in a 1980s documentation. The circuit has a 10-second time delay before firing. The transistor is a general-purpose type and power supply according to the relay.
If the input voltage falls below 12 V the LED glows up. Other voltages can be monitored by...
Found in an old Popular Electronics, this circuit warns when a remote lighting system is not...
This generator is more complete than the previous one, being able to generate pulses as indicated...