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 page shows a crystal oscillator for 2 MHz. Other frequencies can be produced depending on the...
This circuit is from a 1970 publication. The time constant is given by 1.3R x C where R is the...
The supply voltage range of this circuit ranges from 4 to 20 V and the power depends on the chosen...