Two sensors are used in this simple remote-control circuit, one to switch on and one to switch off the relay. The circuit is from 1986 documentation. The transformer has 12 V of secondary.
We have many versions of biofeedback with the 555 IC on this site. This is another one. We found it...
This instrumentation amplifier with differential inputs was found in documentation from the 90s....
Found in an old Popular Electronics, this circuit warns when a remote lighting system is not...