698,430. Railway signalling system for single line sections. WESTINGHOUSE BRAKE & SIGNAL CO., Ltd., MULHOLLAND, E. B., SYKES INTERLOCKING SIGNAL CO., Ltd., W. R., and KING, V. S. Nov. 19, 1951. [Jan. 11, 1951] No. 801/51. Class 105. In interlocking block instrument apparatus. for the control of railway traffic in both directions on a single line between two stations A, Fig. 2 and B, Fig. 3 and comprising a line circuit composed of a single line wire 10 and a return e.g. a wire or earth return between terminals 21, with at each station an operating handle 68 having a lock device 65 which at time is electrically operated to allow movement of the handle between a central normal "line closed" position and a "train going" and "train approaching" position on either side, each station is provided with a pole-changing relay 88 whose circuit includes a contact such as 119, Fig. 3, closed when a train leaves the single line section and a contact such as segment 32, Fig. 30, closed when the handle 68 is in its "train approaching" position 67, the energization of the relay 88 at one station, e.g. B applying appropriate polarity to the line 10 to energize the lock 65 at the other station, viz. A, to permit the return of the handle 68 at station A to its "line closed" position thereby ensuring that no movement of either handle 68 from one of its three positions to another can take place without the cooperation of the operators at both stations. Arrangements for cancelling the proposed train movement after the apparatus has been accordingly set are provided. The operation of the apparatus for dispatching a train from station A to station B will be described. To control the passage of trains in both directions the apparatus at each station will include the circuits of both Figs. 2 and 3. All the references to items at station A. viz. Fig. 2 will bear the suffix "A" and all the references to items at station B, viz. Fig. 3 will bear the suffix "B". Lead wires will be prefixed by "W". Designations of operated or front contacts will be prefixed by f and unoperated or back contacts by b. Battery positive pole at station A will be designated B1 or B2 and the negative pole as N1 or N2 and at station B as B3 or B4 and N3 or N4 respectively. As shown, each handle 68 has rotatable therewith a number of contact segments 23-33 inclusive through each of which contact is made or broken according to the position of the handle. The armature 78 and contact arms of each pole-changing relay 88 are held in the operated position by engagement with a projecting foot 77 of a member 75 which swings about a pivot 84 when the pole-changing magnet 88 is energized with the handle 68 in displaced position. When the handle 68 is restored to its "line closed" position a cam 69 on the handle engages with the latch member 75 to return the member 75 and so allow the contact arms to return to their unoperated positions. After the normal exchange of bell signals key 15 A is depressed to establish a circuit from B1, segment 22A, contacts f 16A, b 13A. galvanorneter 12A, line wire 10, galvanometer 12B, contact b 13B, b 16B of key 15B, w 19B. polar relay 47B, w 37B, w 34B, terminal 21 B, earth return to terminal 21A, w 34A, segment 23A to N1. Polar relay 47B operates normally, i.e. with positive potential on line 10. closing a circuit for the bell 48B over contacts 49B, 50B. Handle 68B is operated towards "train approaching" position 67B and at the commencement of rotation, at segment 29B, establishes a circuit from B3, bell 48B, contacts 49B, 50B, w 55B, segment 39B, w 104B, lower winding of locking device 64B to N3. Device 64B energizes and lifts the locking dog 65B to enable the handle 68B to continue its movement, and at segment 29 opens the circuit of the device 64B to drop the dog back and lock the handle in its position 67B. Signal man A is informed of this operation by deflection of the galvanometer 12A caused by momentarily opening of contact 13B associated with the handle 68H and he releases key 15A. Key 15B is now depressed to operate polar relay 47A "in reverse" by putting B3 on line 10 the energizing circuit of this relay being B3 on contacts b SOB of relay 88B over w 106B, w 116B, segment 25B, w 35B, w 20B, contacts f 16B of key 15B, b 13B, galvanometer 12B, line wire 10, galvanometer 12A, contacts b 13A, b 16 of key 15A, w 19A, polar relay 47A, w 37A, w34A, terminals 21A, 21B, w34B, w36B, segment 24B, w 105B, contact b 83B of relay 88B to N3. Relay 47A closes contacts 49A, 51A and operates the bell 48A. The handle 68A is turned towards "train going" position 70A and at the commencement of the motion, at segment 28A, completes a circuit from B1, bell 48A, contacts 49A, 51A w 54A, segment 28A, w 107A, upper winding of relay 110A to N1. Relay 110A sticks by a circuit from B2 over b 94, w 112, segments 26 W111 and its contact f 108A. At contact f 92A, relay 110 operates the locking device 64A for lifting the dog 65A allowing the handle to complete its movement during which the device 64A is released, the dog dropping again to lock the handle in its "train going" position and by associated contact 13A giving an indication on galvanometer 12B that the handle 68A has been set. Key 15B is then reeased releasing the polar relay 47A which in turn opens the initial energizing circuit for relay 110A. Indicator 38A is now operated over a circuit which exists from B over contacts f 95A, contacts 98A, 99A of cancel device 97A, w 89A contacts b 87A of relay 88A, w 103A, segment 31A, w 46A, terminal 42A, w 41A indicator 38A to N1, and its pointer moves to position 39. Signalman A then operates starting signal lever and when catch-handle contacts 43A, 44A are closed, lever lock 45A is energized to enable the signal lever to operate and clear the starting signal and lever lock proving contact 60 is opened. On entry into the single line section the train opens contact 94A opening the holding circuit of relay 110A which in turn opens the circuit of indicator 38A which returns to its locked position 40A and ensures that lever lock 45A will prevent a second clearing of the starting signal until the required sequence of events has been completed. On leaving the 'single line at B the train closes contacts 119B to complete a circuit for relay 88B over segment 30B and relay 88B is latched in its operated position. A circuit for indicator 115B then exists from B3, indicator 115B, w 116B, w 106B, w 74B, contacts f 73B, w 76B, contacts f 83B, to N3, the indicator moving to red segment 113B to indicate that relay 88B has operated and that normal polarity can now be applied to the line 10. Key 15B is now operated and N3 applied to the line 10 from contact f 83B of relay 88B, over f 73B, w 74B, w 106B, w 116B segment 25B, so that polar relay 47A operates normally to close contacts 49A, 50A and complete a circuit over segment 27A for the lower winding of locking device 64A, to enable handle 68A to be returned to its "line closed" position where it is locked by dog 65A. An indication is given in galvanometer 12B that handle 68A has returned to normal and key 15B is released. Segments 22A, 23A again complete the circuit over which operation of key 15A applies Bl to line 10 to operate polar relay 47B normally, closing contacts 49B, 50B to energize device 64B and allow handle 68B to be returned to its normal position and the latch device is displaced so that the relay 88B releases and the apparatus is in the condition as at the commencement of the sequence of operations. A holding circuit interrupted only when the handle 68 is in the "line closed" position may be provided for the relay 88 in place of the locking device. Suppose now that before the train has entered the single line section at station A, it is desired to cancel that particular train movement. The cancel device 97A, due to mechanical-interlock with the handle 68A can be operated only when the handle 68A is in its "train going" position 70A. The handles 68A and 68B will be locked respectively in the "train going" position 70A and "train approaching" position 67B and neither signalman can energize the line circuit 10 with normal polarity to release the other's handle. Relay 110A is held energized over its stick circuit. If the starting signal has been cleared, it is returned to normal thus closing lever contact 59A. The device 97A, e.g. of 30 seconds delay is operated by turning its handle to open contacts 98A, 99A and, after the delay close contacts 100A, 101A to operate relay 88A from Bl on contacts f 95A of relay 110A and the relay 88A is latched, thereby on operation of key 15A enabling B1 to be applied from contacts f 83A of relay 88A on the line 10-to energize polar relay 47B and subsequently lock device 64B and permit return of handle 68B to its "line closed" position. By reason of known mechanical interlocking means (not shown) the handle 97A must be returned to its normal position with contacts 98A, 99A closed before handle 68A can be moved from its "train going" position. On reception of an indication in galvanometer 12A, key 15A is released and device 97A returned to its normal position, de-energizing relay 88A which however remains latched. Key 15B is then depressed to apply N3 to line 10 over segment 22B to operate polar relay 47A normally and close contacts 49A, 50A, to operate the locking device 64A, and allow handle 68A to be returned to its "line closed" position, unlatching relay 88A which releases and at segment 26A relay 110A is released and the apparatus is back in its normal condition. Instead of treadle-operated contacts 94A, 119B, for applying positive polarity to terminals 93A, 118B respectively, arrangements utilising depression bars or relays energized from the track rails are described.