Patent GB-708045-A (GB)
Title: Telephone systems incorporating bank-position marking in the switching stages
IPC: H04Q3/42
Filed: 1952-07-21
Abstract: 708,045. Automatic exchange systems. AUTOMATIC ELECTRIC LABORATORIES, Inc. July 21, 1952 [Oct. 16, 1951], No. 18380/52. Class 40 (4)  A register-controller transmits for each digit registered an A.C. signal of characteristic frequency to operate a tuned relay in the selector under control, and the selector moves to a position marked by the operated relay. The selectors are 50-point no-normal switches with two sets of wipers, and wiper-switching is determined by the manner of seizure. Non-numerical switching and registration of dialled digits. A calling line is extended over a finder-hunter link to a first group selector provided with a feed relay group with which a register-controller becomes associated. Line relay 310, for example, removes ground from the C terminal of the finders and connects up start relay 410 of the link allotter. The finder 530 steps until the calling line is reached when relay 415, no longer short-circuited, pulls up in series with the magnet. The hunter 630 operates in the same way to seize an idle feed group, and relay 420 pulls up. With 415, 420 both up, switching relay 510 energizes followed by cut-off relay 320, and the allotter advances to the next idle link. In the feed group, line relay 715 energizes followed by guard relay 710. An idle registercontroller is seized over the hunter 700 and relay 720 switches through the talking wires to operate line relay 805 and guard relay 815. The calling subscriber dials on receiving dialling tone, and the dialled digits are recorded on registers 841 ... 845 which are connected up in succession by in-sequence switch 800 under the control of dialling relay 820. Relays 891 ... 894 operate in positions 3 ... 6, respectively, of the in-sequence switch. Control of group selectors.-After the second digit has been registered, relay 891 connects up relay 1855 to start the control. If the first digit is 1-5, relay 1850 energizes over the - wire in series with wiper-switching relay 920 of the first group selector. The latter locks, and 1850 connects, up 1830 over the + wire in series with line relay 930 (lower winding), which locks (upper winding) to the - wire, and opens the original circuit of 920. Relay 1835 follows 1830. If the first digit is 6-0, however, relay 1825 is operative, and 1830 energizes immediately over the + wire in series with 930 (lower) and 1835 makes the circuit over the - wire for 1850 and 930 (upper). The first digit register 841 chooses one of five relays 1801 ... 5 to connect A.C. of a particular frequency over transformer 1800 to the + and - wires. One of five tuned relays 901 ... 5 responds and applies a ground marking in the control bank EC. The selector is started by 930 and self-steps until in the marked position 935 pulls up in series with the magnet and disconnects it, so that the selector steps on to the first outlet of the wanted group. Relay 935 remains locked over multipled contacts of the bank EC, and the magnet has a fresh self stepping circuit over the test wiper as long as busy outlets are encountered. Relay 935 also opens the + wire to release 1830 which ends the first digit control. Relay 1840 energizes in series with 1835 and advances the out-sequence switch 850. If there is no idle line, 935 falls back when the selector moves beyond the wanted group, cuts the drive and closes the + wire to reoperate 1830, which connects up busy relay 745. Relay 720 is disconnected, so that the register-controller is released, line relay 715 reoperates and the calling subscriber receives busy tone. If, on the other hand, an idle line is found, test relay 910 (previously shortcircuited) energizes in series with the magnet, thus stopping the selector, and switches through. The momentary opening of the - wire produces a voltage surge which is detected by a thyratron 1860 (connected up by 1840) and operates 1845. Relays 1850, 1855, 1840, 1835 and 1845 also restore, and 1855 reoperates, provided the third digit has been registered, for the control of the second group selector, which takes place in a similar manner. Control of final selector.-Line relay 1010 and if necessary wiper-switching relay 1075 energize as described above, and one of five tuned marking relays 1001 ... 5 is operated by A.C. of a selected frequency and connects up 1050. The selector self-steps to the marked position in which 1040 pulls up, cuts the drive and opens the + wire to release 1930 in the register-controller, thus ending the control by the tens digit and advancing the outsequence switch 850 to position 5 by the operation of 1840. The tuned marking relay restores followed by 1040, 1050, and 1015 energizes, opening the - wire momentarily to operate 1845 by means of thyratron 1860. Relay 1830 reoperates over the + wire when 1040 goes back and, although disconnected by the release of 1850, 1855, remains up long enough to allow 1835 to reoperate momentarily, bringing about a further advance of the out sequence switch 850 to position 6, in which 1810 pulls up. Relay 1855 re-energizes and remakes the circuits over the - and + wires for 1850, 1830 in series with line relay 1010 in the order determined by 1825, which operates in position 5 if the units digit is 1-5. If that relay is not up, 1030 energizes in the selector and disconnects the first five contacts of each group in the bank EC. One of the tuned relays 1001 ... 5 is again operated by A.C., and since 1015 is now up, an appropriate contact in the selected group is marked in the bank EC. The selector drives as before and 1040 pulls up in the marked position and opens the + wire to release 1830 which moves the out sequence switch 850 to position 7. Busy test and ringing.-If the wanted line is busy, relay 1065 is short-circuited over the C wiper, and 1830 reoperates over the + wire when 1040 goes back and connects up busy relay 745. The register-controller is released as well as the selectors ahead of the first selector, and busy tone is returned. If the wanted line is idle, 1065. energizes over the cut-off relay and releases 1015, 1030. The - wire is thus opened momentarily and the thyratron 1860 detects the resulting voltage surge and operates 1820 (since 1810 is now up), which connects up 735 ' and releases 720. The register-controller is dropped and the connection is switched through at the feed group, relays 745, 750 being connected to the - and + wires on the called side. Meanwhile the called line is rung over ring-trip relay 1055 which energizes on reply and completes the connection, the called line being fed over backbridge relay 1050. The latter closes the + wire to operate 750 in series with 1010 (lower) to effect fourth-wire metering during the release time of 710. P.B.X. hunting.-The C and D contacts are strapped together in the case of P.B.X. lines except the last of the group. The selector is stopped on the first line of a group by 1040, and if it is busy, ground on the C and D contacts operates 1045 in series with 1040 (lower). The + wire is opened to end the control from the register-controller, as described above, but 1040 remains held when the tuned marking relay and 1050 restore, and consequently the selector resumes stepping as long as busy lines are encountered. It stops in any case on the last line which is tested like an individual line. Incoming second group selector, Fig. 11. This has an incoming hold group comprising relays 1110, 1115 in the - and + wires for the control of supervision.