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.
Found in a Popular Electronics from the 90s, this circuit generates signals from 2 Hz to 30 kHz in...
This balance control for the channels of a stereo system was found in a 1969 Mullard...
Pressing S1 stops the circuit. This circuit was found in the October 1992 issue of Radio...