GB809070A - Improvements relating to railway block signalling - Google Patents

Abstract

809,070. Railway signals. SOC. TECHNIQUE POUR L'INDUSTRIE NOUVELLE SOC. ANON. STIN. July 20, 1955 [July 20, 1954], No. 20964/55. Class 105. In a railway block signalling system having stations AB, CD at the ends of a block section wherein the starting signal B or C is returned to stop and locked during or after the entry of a train into the section and cannot be unlocked to be set at clear until an indication that the section is clear is received, in order to enable a train having entered the section and before reaching the exit station to return to the entry station with the home signal A or D at clear, there is provided a device such as a relay 1 having at least one normal or rest position and one operative position which is set into its operative position prior to the departure of a train from the entry station, e.g. A,B, into the section and which in this operative position permits the starting signal B to be set at clear once but prevents resetting of the signal to clear after departure of the train into the section thereby preventing further operation of the block instruments AB, CD until the train, returning to the entry station AB, operates known devices to return the relay 1 to its rest position thereby freeing the starting signal B. The relay 1 in its rest position is held energized and prior to the departure of the train from station AB, a key T having a normally closed contact in the holding circuit of relay 1, is operated to open said contact to release the relay to its operative position in which, contacts (not shown) of the relay interrupt the circuit for the clear position of the starting signal B and stop the operation of the section block instruments. On return of the train to station AB the passing of the train over the insulated track section Is1 completes the pick-up circuit of the relay 1 and the relay assumes its rest position to free the starting signal B. The relay 1 may alternatively be replaced by a D.C. block instrument and members preventing actuation of the initial traffic controlling instrument and the co-operating instrument and of the anti-repeating lock arranged below the initial instrument. The relay 1 may have electrical or mechanical interlock.