Railway vehicle detector in track section - uses Q factor measurement principle with conductor loops between non metallic rails

摘要

A method is used for detecting a vehicle occupying a railway track section. It involves the alteration of the Q factor of a loop laid along that section when a vehicle is in it. The method operates for all vehicles with substantial metallic content, and is not made ineffective by non metallic vehicle wheels or rails. Conducting loops (15,16,17) are laid on the railway track between the rails (10,11), one loop in each sector, and each loop is served by a drive and detection circuit (20,21,22). The drive circuit consists typically of a Hartley type transistor oscillator (25) with the sector loop (16) connected as a load via a capacitance (44). When a vehicle is present, the reduction in the loop Q factor stops the oscillator oscillating. A rectifier (48) and detector (50) attached to the oscillator output monitor this and display the presence of a vehicle in that sector.