This SCR circuit is intended to control an AC load with a low current switch. This switch can be a reed sensor. The load depends on the SCR.
The circuit in the figure is based on an LM101A; diodes can be replaced with equivalents. The...
This circuit, with magnetic sensor, uses an operational amplifier of the time. The circuit is from...
Found in a 90s Popular Electronics, this circuit checks if a remote-control transmitter is...