GB818751A - Improvements in automatic train control - Google Patents

Abstract

818,751. Automatic train control equipment. BRITISH TRANSPORT COMMISSION. Dec. 22, 1955 [Aug. 12, 1953], No. 22230/53. Class 105. Train control equipment automatically operated in accordance with magnetic fields produced on the track when the equipment carrying vehicle passes over said fields includes a receiver containing one or more semi-conducting crystals capable of operating on the "Hall" effect principle to produce an electric current when suitably biased electrically and placed in a magnetic field, the said current produced as the result of the crystals passing through magnetic fields produced in the track being applied to operate audible and/or visual indicators and/or to effect a brake control. The crystals A and B e.g. of germanium, indium antimonide and silicon, in the receiver are magnetically polarised by a permanent magnetic field and when the receiver passes through a field on the track with opposite polarity, the voltages from both crystals A and B applied to amplifiers A, B respectively will be destroyed or reversed so that the amplifiers which receive bias voltages from each other will be made dead and will remain dead when the receiver voltages are restored. A leaky condenser circuit TDA keeps the later amplifying stages of amplifier A alive for two seconds and then the supply from amplifier A is cut off to provide caution indications or brake control. The amplifiers are restored by applying a bias voltage from the driver's reset handle. When the receiver passes through a track magnetic field of opposite polarity, i.e. of the same polarity as the permanent field biasing crystals A, B, crystal C produces a voltage which is applied to amplifier C to cause a resetting bias to be applied to amplifier A. Amplifier A then removes a stopper bias voltage from a later stage of amplifier C which then becomes fully alive for a time controlled by a leaky condenser circuit T.D.C. after the crystal C has passed out of the magnetic field, the output from amplifier C being fed to provide the clear indication. An alternative arrangement is described in which the operation of the cab equipment takes place after the receiver has passed through a magnetic field, the advantage being in this case that if the receiver came to a standstill in the magnetic field, the equipment can be reset if the field is set for a caution indication and the clear indication bell will not ring continuously if the field is set for a clear indication. The amplifiers may be crystals operating on the " Hall effect principle, transistors or magnetic amplifiers.