We found this circuit in a 1967 American documentation. The diodes are general-purpose and the input frequency can be between 80 and 800 Hz.
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...