We found this circuit in an old Mullard (Philips) documentation. The sensor consists of a reed-switch that is coupled to a magnet on one of the wheels of the vehicle.
This circuit makes use of a low impedance microphone. The relay is according to the supply voltage...
This circuit behaves as a voltage controlled resistor and can serve as a small load. The circuit is...
The purpose of this project is to monitor remote loads. The windings are made in a burnt...