Patent GB-563434-A (GB)
Title: Improvements in or relating to electric signalling systems
IPC: B61L25/04
Filed: 1943-02-09
Abstract: 563,434. Electric signalling systems. STANDARD TELEPHONES & CABLES, Ltd., BROWN, A., and MARSHALL, T. A. Feb. 9, 1943, No. 2131. [Class 40 (i)] In a train-describer system, successive descriptions are received and stored in relay groups which are taken into use in cyclic order with the proviso that one group at least must remain empty in order to distinguish the first-stored description. The last-received description may be cancelled, in which case the next description is directed to the same relay group. Each signal denoting a description comprises a constant number of impulses, one of which is reversed in polarity by the operation of one of relays SA, SB ... under control of selecting keys SAK, SBK ... After actuating one of these keys, which also starts impulsing relay MTR, the signalman depresses sending key TK, which connects up relay TPR. The impulses sent are counted by a relay chain CA ... CJ, and when the full number have been sent, relay FPR energizes in place of TPR and bridges relay RC across the line. The latter responds to an acknowledgment signal from the receiver and disconnects relay MTR, so that the lamp SAL, SBL ... corresponding to the selection lights steadily instead of flashing. If no acknowledgment signal is received, lamp FIL lights. The operated selecting relay remains locked until a fresh description is set up, or until reset key RK is actuated. Key SKK and relay SK correspond to a cancelling signal, which is sent and acknowledged like the description signals, except that relay FPR remains locked after the relapse of MTR until a further signal of reversed polarity is received to operate relay AC, which causes a buzzer to sound. At the receiver, the impulses are received by oppositely-polarised relays IP, IR and are distributed by a counting chain CA ... CE to a relay-group AA ... AD in which one relay becomes energized corresponding to the selecting relay at the transmitter. Provided the number of impulses is correct, relay OK operates and sends the acknowledgment signal. If a cancel signal is received, relay AD connects up relay CAR to provide a circuit for relay KAN when the cancelling key KAK is pressed and a signal of reversed polarity is reverted. The storage relay groups DAA ... DAC, DBA ... DBC, &c. are each provided with a master relay MDA, MDB, &c. which is energized when the relay group holds a description and with a sequence relay SCA, SCB, &c. which is energized when the relay group is to receive the next description, these relays being interconnected so that the groups are used in cyclic order. The transfer from the relay group AA . . . AD takes place when relay OK operates. In order that the first-stored description shall be distinguished, one more group than the maximum number of descriptions is provided, and when all but one of the groups are occupied, relay RFR energizes, isolating the receiver and operating relay RF over the line to light lamp RFL and disconnect the selecting keys at the transmitter. The clearing out key COK controls relay CSR to remove the earliest-stored description, which is immediately behind an empty storage group. Similarly, the cancelling key KAK controls relay KAN to remove the laststored description, which is immediately in front of an empty storage group. Only the first and second descriptions are displayed on lamps AXL ... CXL, AYL ... CYL, which are controlled by the master relays so that after a clear out the second description is stepped up to the first display position, while the third description appears in the second display position.