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 control for motors with current up to 1.5 A was obtained in a 1989 publication, but it can...
This circuit was found in a 90s Wels' Think Tank. The frequency depends on C2 and R3. The handset...
This circuit is from an old documentation but still current for assembly. Just use BC548 instead...