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 doubles and reverses the polarity of voltage Ve which can be between 5 and 15 V. The...
This circuit includes the amplifier for the signals, being fully transistorized and using varicap...
This circuit was found in an American 1980s documentation. The integrated circuit used is uncommon...