Patent GB-374944-A (GB)
Title: Improvements in or relating to electric signalling or selective systems
IPC: B61L7/08
Filed: 1931-03-19
Abstract: 374,944. Electric signalling systems. STANDARD TELEPHONES & CABLES, Ltd. and DAVIS, W. R., Connaught House, Aldwych, London. March 19, 1931, No. 8446. [Class 40 (i).] In a system, such as a train-dispatching system in which station selection is effected by transmitting a code of 17 impulses divided into three trains, the code is set up on relay registers, but in order to avoid the provision of sufficient relays in each register to take the largest digit (13), three smaller registers of equal capacity (7) are provided, one of which is replaced by an additional register of larger capacity (13) when required. The registers are set from a keyboard and impulses alternating in polarity are sent out under the control of a counting chain which is adapted to control the counting of a digit commencing with an impulse of either polarity. The registers and counting chain may be used in a system controlled by reverting impulses. Provision is made for cancelling a stored code. Registration of code, say 692. The lead to the grounded contact of relay F, Fig. 2, is used as a holding wire for the relays of the registers, Fig. 1. Momentary operation of key K6 energizes the lower winding of A6 which holds over its upper winding, and an initial circuit is completed for two-step relay D1 which operates fully, on restoration of the key, to transfer battery from the lower windings of the A relays and relay H1 to the B relays and relay H2. As the second digit exceeds 7, the B relays are not affected by operation of key 9, but this key operates C9 in the auxiliary register C8 .. C13 and the marking of this relay is made effective for the second digit by the operation of H2 over the key. Relays C9 and H2 lock up, and two-step relay D2 transfers battery to the C relays, C2 being operated by key K2 on the restoration of which two-step relay D3 completes the circuit of pulsating relay PR, Fig. 2, and connects battery across leads extending to the contacts of impulse relay P. Transmission of impulses. The chain 21, 22 .. 33, 34 performs three cycles in succession a digit being sent during each cycle, the odd impulses (P operated) being counted by the lower row and the even ones (P released) by the upper row. The marking contacts 2a .. 7a of the A relays, and the marking contacts auxiliary register C8 .. C13 made effective over 8a .. 13a if H1 is operated on the first digit, are connected to contacts 22a .. 33a of the counting relays. The corresponding contacts of the B relays and of H2 are connected to corresponding contacts of the chain over change-over contacts of relays L1, L2 to provide for digits commencing with a make or break as will appear later, and marking contacts for the third digit are similarly connected up over relays L3, L4. The first ground impulse from relay PR passes over a chain of contacts of the even relays to relay 21 which operates and prepares a circuit for 22 so that on termination of the impulse 22 energizes in series with 21. The next impulse passes to 23, relays 24, 23 operate in series and release 22, 21 when the impulse terminates, and the chain runs through a cycle in similar manner. Relay PR also sends impulses to P which sends impulses to line in the form of current reversals. As the first digit is 6, relay 26 on operation connects marking ground on 26a (connected to 6a of A6) to E1 which opens the circuit of P (unoperated at this time) and locks over contacts of S1, S2. The chain runs on and when 32 operates it completes an initial circuit for two-step relay S1 which operates fully when 24 releases 32, with the result that (1) battery from a contact of S2 on the a backcontacts of the relay chain is transferred to the b back-contacts and (2) E1 falls back to prepare the circuit of P for the first impulse of the next digit. As this digit (9) is an odd one, it terminates with P operated and relay 29 connects marking ground on 29b (connected to 9b of H2) to 02 which locks up and holds P. When 34 operates, it completes an initial circuit for relay S2 from the grounded back-contact of 21, so that when 21 is operated by the next impulse, S2 operates fully and (1) transfers battery from the b back-contacts of the chain to the c backcontacts and (2) releases P. Relay P has therefore been held up until the first impulse of the third cycle has operated 21 so that this impulse has been absorbed. The third digit thus commences with a relapse of P and, simultaneously, the operation of 22 due to a break by PR. As the first impulse to the chain has been lost as concerns the signalling line, the marking leads from the third digit register must be moved forward on the counting chain and this was done by relays L3, L4 which operated and locked when 02 operated. The third digit (2) is therefore terminated by the operation of 03 when 23 pulls up on the third impulse to the chain. P remains operated (ringing period at wanted station) until the chain runs down to 34 which operates F to release P and the registers. The relapse of P sends a release signal to the distant selector. Cancelling an incorrectly set-up code is effected by key CK which operates F to release the registers. General call. Momentary operation of key GCK operates two-step relay D3 to connect battery across the impulsing contacts of P and start PR, and operates GC to mark contacts 23b, 22c. There is no first digit marking so that the chain runs on until 23 is operated on the second cycle to count a continuous train of 17 impulses. During this period 32 completes an initial circuit for S1 (over the lower contacts of GC) and when 34 pulls up S1 operates fully to prepare the stopping circuit normally used for the second digit so that when 23 pulls up after 17 impulses, 02 pulls up and holds P until this relay is released and S2 fully operated by 21 on the third cycle as previously described. When 22 operates on this cycle (P still inert), the marking on 22c operates E3 which maintains P de-energized. At the end of the third count F pulls up as before and restores the circuits to normal.