Patent GB-523940-A (GB)
Title: Improvements relating to railway traffic controlling apparatus
IPC: B61L23/16
Filed: 1939-01-18
Abstract: 523,940. Railway signalling systems. WESTINGHOUSE BRAKE & SIGNAL CO., Ltd. Jan. 18, 1939, No. 1813. Convention date, June 22, 1938. [Class 105] A wayside and cab signal system, controlled by rail or line wire code current varied in the length of the current pulses and in the interval between pulses, has de-coding relays of the slow response type which respond only if energized for approximately half the complete period of pulse and interval, however short the cycle period may be. A three-aspect wayside signalling system is shown in Fig. 1, but arrangements are also described giving up to six aspects and for cancelling a level-crossing signal as soon as the level-crossing sub-section is vacated, these arrangements in some cases using, in addition, the " frequency " effect of the code pulses. Fig. 2 shows the different codes which are given by cams of a motor-driven code transmitter. In the normal state of the arrangement shown in Fig. 1, a code transmitter CT applies alternating-current code LL (long pulse and long interval) to the rails through a front contact 6 of a de-coding relay BQ. The track relay TR follows the code and thus its vibrating contact 7 applies direct current to the 'halves of a de-coding transformer DT the secondary winding of which on the positive half-wave (track relay TR closing its front contact), energizes de-coding relay FQ and on the negative half-wave (track relay closing its back contact 7) energizes de-coding relay BQ. Since code LL is applied, the relays BQ, FQ are each energized for half the complete period of pulse and interval and therefore both these relays lift and their front contacts 27, 26 light the lamp G of the wayside signal Se. With section EF occupied, the track relay remains dropped and thus the de-coding relays BQ, FQ are both dropped. The back contact 27 of relay BQ lights the lamp R of the wayside signal Se and the back contact 6 causes code SL (short pulse long interval) to be applied to the rear section. The code SL does not give, in a complete period of pulse and interval, a sufficiently long feed to the right-hand half of the de-coding transformer DT so that the positive half-wave from the secondary winding is not effective to lift the relay FQ. The long interval, however, gives a sufficient feed to the left-hand half of the de-coding transformer for the negative halfwave from the secondary winding to be effective to lift the relay BQ. With relay BQ lifted and relay FQ dropped the front and back contacts 27, 26 light the lamp Y of the wayside signal and the front contact 6 applies the clear code LL to the rear section. The de-coding relays FQ, BQ, are shown fed through rectifiers 8, 10 at location E but can be fed through a mechanical rectifier such as a contact 18 of the codefollowing track relay TR as shown at location F. For cab signalling similar apparatus is used, a code-following relay inductively operated from the coded rail current being substituted for the track relay. In the higher aspect signals an auxiliary slow relay is provided to prevent a flashing of an incorrect signal during a change of aspects, Fig. 10 (not shown). The code currents may be transmitted over a line wire circuit which includes front contacts of a track relay of a simple track circuit, Fig. 12 (not shown). Specification 284,384, [Class 105], is referred to.