Patent GB-661118-A (GB)
Title: Improvements in or relating to automatic telephone systems
IPC: H04Q3/00
Filed: 1948-11-23
Abstract: 661,118. Automatic exchange systems. AUTOMATIC ELECTRIC LABORATORIES, Inc. Nov. 23, 1948 [Dec. 8, 1947], No. 30413/48. Class 40 (iv). In a director system in which access is had to a director from certain levels of the first selectors a relay-type director-finder allots idle directors in turn to the selectors. The second digit of the two-digit office code is translated into from one to five routing digits which are transmitted to the second selector. The system described caters for three classes of subscriber: unrestricted, partially restricted (i.e. calls to own zone only), and fully restricted (i.e. local calls only). Apparatus is also described for testing the operation of the directors. Fig. 1 shows the general lay-out of the exchanges in the system with the office code digits of each exchange. Local calls in exchange J. (Figs. 4-10). A subscriber C (Fig. 4), wishing to call subscriber C1 may dial either the three numerial digits only or the two-digit office code (77) of the exchange J followed by the numerical but is re-operated by ground on 572 as soon as any director becomes idle, then if all the directors are not busy reset relay 590 pulls up and energizes all allotter relays corresponding to idle directors. The operation of any of the allotter relays releases 580 and 590. The start relay chain circuit is arranged so that if two start relays are energized simultaneously, the one nearer the battery through 520 is the only one which operates fully and locks. Thus two selectors are prevented from seizing the same director. Seizure of director. Assuming that the director shown is idle connect relay 510 pulls up, locks, and short-circuits the connect relays of the other second selectors. The calling loop is extended to the director line relay 610 which operates, and relays 410 and 640 pull up. Relay 510 also grounds conductor BY of cable 500 to busy the director to the test circuit of Fig. 10. The operation of relay 410 digits. In the first case a first selector FS and a connector CS respond to the first digit and the last two digits respectively in the usual manner. In the second case the first. selector is stepped to the seventh level and hunts for an idle second selector SS. Line relay 430 which operates to the calling loop brings up release relay 440, start relay 530 of the director-finder DF (Fig. 5), and guard relay 520. Relay 440 grounds conductor 52, and operates change-over relay 450; and relay 530 disconnects the other start relays, e.g. 540, 550, and brings up the connect relay corresponding to the director allotted. Allotment of directors. If the director. shown in Figs. 6-9 is idle allotter relay 560 is held energized over its upper front contacts, and similarly if the directors (not shown) corresponding to relays 567, 568 and 569 are idle these relays will also be operated. Idle directors are allotted in the order of their allotter relays 560, 567, 568 and 569, and when a director is taken into use its release relay (e.g. 620) is operated as described below and releases the allotter relay. When all directors have been allotted relay 580 pulls up, and as 570 is released when all directors are busy releases 530 and 520, and transfers line relay 430 from the calling loop to the director pulsing contacts 959. Release relay 620 is operated by 610, and 410, 640, and 510 hold up. Relay 560 falls away to preselect the next idle director. Second digit dialled. If the second digit is dialled before an idle director is seized (410 down) line relay 430 responds and steps the second selector to the corresponding level. Operation of the vertical off-normal springs 482 brings up 460 and when change-over relay 450 relapses at the end of the train 460 interacts with the rotary magnet 470 to drive the wipers to the 11th position where cam springs CS and CS1 operate to prevent re-operation of the rotary magnet and revert busy tone. On the first rotary step the rotary off-normal contacts 472 open the start circuit to 530 which releases the director-finder thus preventing seizure of a director and operation of relay 410 in the second selector. The calling subscriber hangs up and initiates the release of all the equipment. In the normal case (410 up) the line relay 610 responds to the  second digit (7), repeats it to switch U, and brings up 630 for the duration of the train. Relay 630 energizes the drive magnet 825 of the sequence switch SC which steps SC to position 1 and at its front contacts energizes both windings of relay 600 in parallel. Relays 600, 670, 680 and 690 are differential relays which do not operate in these conditions, but are operated to close their X contacts only by an inductive kick when the energizing ground on conductor 616 is removed. The relapse of 630 releases magnet 825, whereupon 600 closes its X contacts and completes a series circuit for both windings from hold conductor 615. Relay 600 then operates completely, brings up coding relays 700 and 720 in series, transfers the energizing circuit to the second kick-up relay 690, transfers the impulsing circuit to the hundreds storage switch H over conductor 634, and brings up 910 over SC in position 1. Relay 700 locks up, operates 760, and prevents operation of 770, while 720 and 760 bring up digit-skip relay 940 over SC in position 1 and conductor H of cable 800. Relay 940 short-circuits the pulsing contact 959 and grounds the stop conductor L1. The operation of 910 energizes relay 953 which locks under control of 950 and brings up 955 which opens the pulsing contacts 959 and operates 950 and the first counting relay 972. Relays 953, 955 and 950 then release in turn and the cycle is repeated until ground is removed from conductor 638 by the operation of stop relay 920. On the operation of counting relay 972 the ground on conductor L1 is extended to the upper winding of 920 and the two windings of 930 in parallel. When 955 restores, the short-circuit around 960 is removed and 960 pulls up in series with 972 to transfer the counting circuit from the ODD to the EVEN conductor. The operation of stop relay 920 in the above circuit steps the sequence switch SC to position 2, holds 950, disables 953 and releases the operated counting relays 972 and 960, followed by 950. Ground is thus removed from the lower winding of 930 which thereupon operates, locks up 940 over its lower winding, releases the sequence switch magnet 825, re-operates 953, and shortcircuits contacts 959. Relays 955, 950, and 972 pull up in turn and the 'grounded conductor L1 is connected to the lower winding of 920 which thereupon restores. Relays 953, 972 and 960 fall away, and the resulting disconnection of L1 releases 930 followed by 950. Operation continues in this manner until the wipers 820 and 821 of SC reach position 6 where the circuit of 910 is opened provided the hundreds digit has not been dialled, and the relapse of 910 disables 953 to prevent further cycles. Digit-skip relay 940 is operated over wiper 820 in positions 1 to 5 in order that the sequence switch may be stepped quickly to position 6, all routing digits are skipped and the director is ready to transmit the numerical digits. Third digit dialled. Line relay 610 responds and the digit is registered on the hundreds switch H (Fig. 8). Kick-up relay 690 pulls up at the end of the train and re-operates 910 over wiper 821 in position 6. Interrupter relay 953 then initiates the transmission of the hundreds digit. The counting relays operate in the order 972, 976, 986, 991 and 901, 960 switching the counting circuit from ODD to EVEN conductors and vice versa, and 963 coming up at the end of the fifth cycle whereafter the counting relays are re-operated with 963 up in the sixth to tenth cycles. The stop leads L1 to L9 are extended to 920 in the first to ninth cycles so that if one of them is grounded by the wiper 820 the transmission is stopped. In the tenth cycle ground over front 901 and front 963 operates 920 directly. Fourth and fifth digits dialled. The fourth digit is stored on the tens switch T, relay 630 operating release magnet 816 of the units switch U, and kick-up relay 680 coming up at the end of the train when 630 relapses. The fifth digit is stored on switch U and 670 comes up in like manner. Transmission of numerical digits. With wiper 820 in position 6 digit-skip relay 940 is released and as the counting relays are operated in turn the pulsing contacts 959 transmit impulses to line relay 430. When the marked L lead is connected up after the required number of impulses have been sent 920 pulls up, stops the transmission and steps the sequence switch to position 7. The operated counting relays fall away, 930 pulls up and grounds L7, and 950 restores. The interrupter relays start operating again to cause the counting relays to count up to seven (930 having short-circuited pulsing contact 959) and on the second operation of 976 with 963 and 966 up the ground on L7 restores relay 920 to stop counting. This counting period constitutes the inter-digital pause. The tens digit is then transmitted in like manner relay 910 being operated over wiper 821 in position 7. Another inter-digital pause is counted off and then the units digit is transmitted. The sequence switch steps to position 9 where cut-off relay 650 operates over wiper 820, connects the busy lamp BL to interrupted ground on conductor 627, and shunts down 410 in the second selector SS. Setting of selectors. Line relay 430 responds to the hundreds digit and selector SS hunts for an idle connector in the selected level whereupon relay 420 pulls up and switches through the pulsing leads. The seized connector selects the wanted line in response to the tens and units digits. The relapse of relay 410 releases connect relay 510 and completes the talking connection. Relay 510 initiates release of the director.  Outgoing calls. To call a subscriber in exchange C a subscriber at exchange J dials the office code " 79 " followed by th