Patent GB-542078-A (GB)
Title: Improvements in or relating to train describing signalling systems
IPC: B61L25/06
Filed: 1940-04-19
Abstract: 542,078. Electric signalling systems. STANDARD TELEPHONES & CABLES, Ltd., BROWN, A., and MULLARKEY, A. J. April 19, 1940, No. 7097. [Class 40 (i)] In a train describing system, a signal cabin may have a receiver for incoming descriptions and a number of transmitters for passing on descriptions which may be for trains over different tracks, or it may have a number of receivers and a single transmitter or a number of receivers and transmitters, and according to the invention means are provided for selectively transferring automatically or semi-automatically a description stored in a receiver to code determining equipment of a transmitter whereby the description may be re-transmitted. The selection and the initiation of the re-transmisson may be effected manually or by passage of the train over the tracks, or the selection may depend on the nature of the stored description. Manual control is described.in detail. Transmitter, Figs. 1 to 3 ; normal operation.-The code is. set up on relays SA ... SU by keys SAK . . . SUK, the relays being held over relay ALO which operates MLO. Operation of the " transmit " key TK energises TRG so that when the key is released TS pulls up, operates the motor start relay MS and clutch magnet SM of the control sequence switch and energizes RFR which connects the contacts of impulse relays IS, IPS to line L1, L2. Impulse relay IS is steadily operated over cam U to send a long " prepare " pulse until the sequence switch reaches position 3 whereupon it is impulsed twice per position by cam V the makes which extend over “ of a position being centred on 3¢, 4, 4¢ and so on the polarity of the impulse in each case being, determined by non-operation or operation of the corresponding code relay SA ... SU. When the relay is operated, a circuit over the left-hand winding of IS in series with IPS prevents the operation of IS over its right-hand winding by cam V until IPS has operated and opened the LH circuit of IS. At the end of the impulse, IPS is held over its R.H. winding until IS has released. Relay IPS reverses the polarity of the impulse source, the change in both directions being effected while IS is unoperated. When the code has been transmitted, the sequence switch stops in position 16 in which FPR is operated, until a checking signal of reverse polarity sent back by the receiver operates relay RC which causes the switch to go to position 1, the relay group LA ... LU which has been storing and indicating a preceding transmission being released at cam I and re-set over cam G in accordance with the code which has just been transmitted, the code relays SA ... SU being eventually released at cam G. When the receiver is full, normal polarity operates RF to give an indication and prevent further operations at the transmitter. Dealing with faults.-The switch remains in position 16 and a fault lamp (not shown) is lit steadily over contacts RC and FPR instead of momentarily as in the case of a successful transmission. The signalman thereunon throws fault clearing key FK operating CFG followed by CF on restoration of the key. Relay CFO pulls up and causes the switch to proceed to position 1. CF and CFO relapse when the switch leaves position 18, but TS has been held so that the transmitter makes a second attempt to transmit the code. The' previous transmission stored in relays. LA ... LU is not interfered with since CF holds these relays and also prevents transfer of a record from SA ... SU. If re-transmission of the code is not desired, the re-set key RK is pressed when the switch stops in position 16. Relay CKR pulls up followed by CF to send the switch to position 1, but as TS is not held the code relays will be released. Receiver, Figs. 4 to 6.-Impulse relays IR, IP respond respectively to pulses of normal and reversed polarity, and during the " prepare " pulse guard relay RG and its relief RGA pull up and apply +<SP>ve</SP> to the points marked P. Relays DCR operates and O follows when IR relapses. Relay OB lights a lamp to indicate that a transmission is being made and should be extinguished if no fault is present. On re-operation of IR or IP the first make impulse of the code, a shunt on relay OA is removed and this relay operates in series with O so that at the end of the impulse E pulls up, holds independently of OA, and releases O, OA. On the second make impulse E is released and O re-operated at the end thereof this operation being repeated on subsequent impulses. The impulses are counted on chain CA ... CX, CA being operated by O on the first break impulse and CB in series with CA when O falls back on the second break impulse. CB extends the circuit to the next pair and all relays lock up. The relays of the chain prepare successive circuits for the code relays AA ... AV which are operated by IP if the following make impulse is of reversed polarity. A complete transmission comprises 21 make impulses (20 code characters and 1 extra to provide for cancelling) and 22 breaks so that 22 relays CA ... CW of the chain should be operated to energize OK which sends back the checking pulse of reversed polarity. Assuming that the first display storage group BA ... BU, Fig. 5, is available, the code stored in AA ... AV is transferred thereto over a circuit including cam F of a sequence switch in position 1, and the operated relays and series relay MB lock up. On termination of the transmission, guard relay RG and all other relays in the code receiver proper relapse. The release of OK operates UA which is the first of a series of relays controlling chain circuits for transferring subsequently received descriptions to further display groups such as DA ... DU of which six are provided. When the display groups are full, relay UF, Fig. 6, operates UGA which connects normal polarity to the line to provide an indication at the transmitter. Removal of first display and stepping up the remaining displays.-The signalman throws key COK, Fig. 4, whereupon CRG, CSR pull up in turn on operation and release of the key, CSR being temporarily held over cam E. The stout relay MS and clutch Z of the sequence switch are operated and the switch makes a complete revolution controlled by cam A. In positions 3 to 4, the first display group BA ... BU is released at cam G and the display is transferred from the second group to the first, and in subsequent positions of the switch similar release and transfer operations follow for other displays. All the lamps are dimmed during the transfer period by means of a cam, not shown. Cancellation from transmitter of an incorrect display.-The cancel key CAK, Fig. 1, operates CAG followed by CAN on its release. Relay TS pulls up and starts the transmitter which sends 21 impulses as before, the last of which is of reversed polarity. The automatic checking signal is received while the transmitter is waiting in position 16 and RC is operated but contacts of CAN prevent the transmitter from proceeding to position 1 and maintain a "cancel" lamp lit to remind the signalman. When the receiving signalman acknowledges the cancellation, he sends back a pulse of normal polarity which operates AC whereupon CAN falls back and the transmitter proceeds to normal and the description displayed by the " last sent " group LA ... LU will be removed. At the receiver, the cancel code operates relay AV, Fig. 4, and CAR is now operated in parallel with OK to give visual and audible alarms (not shown). OK locks up in the present case. The receiving signalman acknowledges by using key KAK which on operation and release causes KAG, KAN and CAA to pull up and hold. Relays CAR, OK, KAG, KAN and CAA fall back in turn. During a period, mainly the release time of KAG. KAN applies the acknowlelgment pulse to the line and relay' CAA applies a pulse over chain contacts of the U relays, Fig. 5, to shunt down the last occupied display group, the U relays being temporarily held by CAA to prevent successive shunting of the display groups. Re-transmitting control arrangements, Figs. 7 to 9.-The arrangements are such that descriptions displayed in any of 3 receivers A, B, C, individually associated with three incoming tracks may be re-transmitted from any of 3 transmitters X, Y, Z for 3 outgoing tracks. Nine re-transmission keys AXK-CZK, Fig. 7, are provided, and a re-transmitted description may be cleared automatically or await clearance by the signalman. In the latter case, operation of a further re-transmission key associated with the same receiver selects the first description which has not been transmitted. A lock-out circuit prevents more than one re-transmission circuit being effective simultaneously but it might be arranged that independent re-transmission circuits such as A to X and B to Y should be effective at the same time. The lock-out does not persist during actual code sending. It will be assumedthat re-transmission from A to Y is required. On throwing key AYK, relay AY pulls up in series with relay RLO in a circuit including contacts of MLO of transmitter Y (idle), RAP, Fig. 9 (receiver A with a stored description), sequence switch cam O of receiver A in position 1 and contacts of AA, AC, Fig. 7, which indicate that no re-transmission is in progress from receiver A. Relay AY open chain operating circuits of all other key relays and RLO disables the keys COK, Fig. 4, of the receiver to prevent removal of a display during re-transmission. The key relays have to control numerous contacts and are provided with relief relays (not shown). The cross connections between receivers and transmitters are shown in Fig. 8 and it will be seen that relay AY connects contacts of the first display group BA ... BU, Fig. 5, of receiver A to the code relays SA ... SU, Fig. 1, of transmitter Y. Relay AY also operates YG, Fig. 8, and remains held until MLO, Fig. 1, operates or the signalman restores key AY. When this occurs transmiter relay TS, Fig. 2, pulls up and transmission takes place as previously descr