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 was found in a General Electric documentation from 1966. It uses discrete components...
The CMOS TLC555 [equivalent to the bipolar 555] can be used as a monostable in the configuration...
This small audio amplifier was found in an American publication in 1975, The integrated circuit used...