GB488240A - Improvements in railway track circuits - Google Patents

Abstract

488,240. Railway signalling systems. GENERAL RAILWAY SIGNAL CO. July 21, 1937, No. 20249. Convention date, Aug. 21, 1936. [Class 105] The supply to a track circuit with a directly connected track relay which is maintained energized consists of voltage pulses having a steep wave form and of short duration relatively to the time space between the pulses. Such a supply may be derived from a normal sinusoidal wave form supply by a transformer having a secondary winding 8 on a core limb which becomes saturated..In parallel to this limb is a limb 10 with an air gap. When a supply from the generator G and of normal sinusoidal wave form A, Fig. 3, is applied to the primary winding 7 of the transformer the fiux in the secondary limb is of the wave form B and so the secondary winding 8 gives the spaced voltage pulses C of steep wave form and alternating in polarity. For direct-current track relays the transformer secondary is connected through a rectifier to allow only unidirectional pulses. This latter arrangement provides for ballast compensation in a manner similar to the arrangement described in Specification 445,515,