This circuit was found in the Electronics Experimenter Handbook from 1991. The sensor is a diode and the circuit has a relay according to the voltage used in the supply.
This ultra-low frequency receiver circuit was published in the August 1973 issue of Radio...
Maxim MAXREFDES67 Universal Analog Input Micro PLC is ideal in factory automation because of its...
The sensor of this circuit is an NTC with a resistance between 200 and 1000 ohms. The resistor R1 must...