Patent GB-496138-A (GB)
Title: Improvements in or relating to telephone systems
IPC: H04Q3/00
Filed: 1937-05-24
Abstract: 496,138. Automatic exchange systems. ASSOCIATED ELECTRIC LABORATORIES, Inc. May 24, 1937, No. 14441. Convention date, June 19, 1936. [Class 40 (iv)] In an all-relay finder-connector link, the finder comprises tens connecting and test relays 120 ... 122, 130 ... 132, &c., operated by tens relays 552 ... 556 in the allotter and units relays 210 ... 250 which operate in succession, testing the lines in the selected tens group two at a time. The final selector comprises tens connecting relays 420 ... 422, 430 ... 432, &c. and units relays 310 ... 350 controlled by an impulse responder 810 ... 860 which is individual to the link and also takes a ringing digit. Each of the units relays is associated with two digits and acts in conjunction with a discriminating relay 360. In both switches there is a pair of connecting relays for each tens group, one or other being actuated according as the units digit of the calling or wanted line is or is not greater than 5. Each line circuit has a relay such as 50 for locking it clear of the exchange circuit in the case of reverting party line calls and forced release. The final selector hunts in certain groups for ring-down and for automatic twoway junctions. Call-finder. When a subscriber calls (but not when either side of his line is grounded) his shunt-field line relay such as 70 energizes one of a set of relays 552 ... 556 in the allotter in accordance with the tens digit of the calling number. This relay energizes 551 which prevents interference by calls from other groups and completes circuits for the associating relay 170 of the preselected link and for the appropriate tens relay 122, 132, &c. in that link. The relay 122 &c. extends the test wires of all the lines in the group to the units relays 210 ... 250, Fig. 2. At the same time a circuit is made for 558 in series with 630 and the units relays then operate in turn somewhat sluggishly, each one connecting two test leads to the common test relay 557 and the individual test relay 270 respectively. When the calling line is reached, either 270 or 557 pulls up in series with the calling cut-off relay such as 60 which energizes the lock-out relay 50 to break the start circuit. The test relay energizes the appropriate one of the pair of talking circuit connecting relays 120, 121, 130, 131, &c. If the finder fails to find the line, the link is released as described under " Standstill release &c." below. Release of common circuit. Allotting new link. When No. 1 link is idle, 501 is locked energized as shown in series with 591. When the operation of the finder is complete a circuit is made by the group connecting relay over 184 and relay 502, corresponding to the next link, for 594 which locks, energizes 597, and releases the associating relay 170 of No. 1 link, whereupon 558 and 557 (if operated) fall back. 502 unlocks 501 and locks itself instead in series with 591. It also connects the guard lead of No. 2 link to 503. If this link is busy 503 unlocks 502 and so on until an idle link is reached. Removal of the marking potential by relay 50 releases the operated relay 552, 553, &c. and this releases 551. All links busy. In this case all the multiple ground connections to 592 are broken and its relapse prevents further hunting by the allotting relays 501 ... 506, energizes 597 and connects up a tone circuit 98 to give the busy signal to any incoming junction call. 597 energizes 596 which operates 595 and releases 594. 595 energizes 593 which releases 597. 597 releases 596 at once and 595 after a considerable delay imposed by the oscillation of its armature between contacts 598, 599. 595 on falling, releases 593 which then re-operates 597. This cycle continues until a link becomes available. As soon as this happens, 592 pulls up, opens the tone circuit and completes the hunting circuit for the link allotting relays 501 ... 506. Selection cf local line. On the operation of the associating relay 170, line relay 630 is operated in series with 558 and energizes release relay 620 and relay 680 which are followed by 720, 710 and 608, 710 shunts the other line relay 610, starts the tone machine, and connects up dialling tone lead DT, Fig. 8, to the condenser TC, Fig. 7. Cn the operaticn of the connecting relay such as 120, the calling locp is extended to relays 610, 630 and the subscriber hears the dialling tone. 630 responds to dialled impulses and at each relapse brings down 680. A priming circuit including 680, 630, R4 makes 630 pull up quickly when the loop is re-made. 680 on falling for the 1st impulse energizes 640, 660, 670. 670 holds itself and 660 until the end of the digit and 640 grounds the odd wire 655 to energize the 1st counting relay 810. Re-operation of 630, 680 at the end of the impulse causes holding of 640 and operation of 650. Relapse of 680 at the second impulse unlocks 640 and holds 650 and ground is thus connected to the even wire 656 to operate the next counting relay 820. At the end of the impulse, 650 is released and at the beginning cf the 3rd impulse, 640 is re-operated. Each counting relay on operation releases the preceding one except that the 6th leaves the 5th operated until the second operation of the 1st and itself remains locked up until after the marking operation. Relay 400, on energization by the first operation of 660, locks up and connects the final selector tens relays 420, 450 &c. to the appropriate counting relay contacts. At the end of the first digit, the relapse of 670, 660 brings down 640, 650 if necessary and operates the selected tens relay which locks up, connects all the test leads in the selected tens group to contacts of the units relays 310 .. 350, and energizes 880 over back contacts of these relays and the lead 12. 880 locks, cuts off dialling tone and unlocks 500 whereupon the operated counting relay or relays fall back. The units digit controls the impulse responder in the same way as the tens digit but in this case the marking circuit goes to the units relays, 370 being energized when 660 pulls up at the beginning of the digit. Each units relay marks two lines, discrimination as to which is to be called being effected by the energization or non-energization of 360. Operation of any units relay energizes 870 which locks and releases 370, whereupon the counting relay or relays fall back. Busy test and party-line ringing. The impulse responder is actuated by the ringing digit as by previous digits but in this case the operation of 660 releases 880 and energizes 700 which energizes 726 and shunts 610 independently of 710. At the end of the digit, when 660, 670 fall back, 726, 710 are released and a test circuit is completed before 726 has time to fall from 663 through 770 and the cut-off relay such as 471 of the wanted line. If 770 does not operate, the busy signal goes back from BT. If tl:e line is idle however 770 locks, starts the ringing generator, releases 700 and operates the appropriate tens connecting relay. 700 on falling removes the shunt from 610 and connects the ringing start relay 790 to lead 659 which is grounded at the beginning of each ringing cycle. 890 completes the ring-back tone circuit and connects the selected ringing leads to the talking circuit via ring-trip relay 780. As shown, half the parties have their ringers connected to each leg and selection between parties on one leg is by code or frequency. Completion of connection and release. Ring trip relay 780 on operation disconnects the ringing circuit and connects the called line back to the supervisory relays 750, 613. Relay 750 releases 608 and energizes 740 which locks, stops the ringing machine, energizes 600, and releases 870, 890. 600 reverses the calling side feed. When the called party hangs up, 750, 613, 600 fall and 608 pulls up again and when the calling party hangs up, 610, 630, release relay 620 and all the other operated relays fall back. Reverting party line calls. The calling subscriber on hearing busy tone restores his handset and line and release relays 610, 630, 620 fall back. The cut-off relay however is held over the calling end of the link, 364, 703, 681, and relay 720, which is in parallel with the cut-off relay over the answering end of the link, is held also. On the relapse of 620, 730 is connected in parallel with 720 and the cut-off relay. 730 locks, holds 720 and the cut-off relay, energizes 770 and releases the tens relay such as 120. 770 releases 700 and energizes the appropriate connecting relay. The line is then rung as previously described and the operation of ring-trip relay 780 and supervisory relays 750, 613 is followed as usual by the release of 608, 870, 890 and the operation of 608, 740. Since 730 is energized however, the operation of 740 releases 720 to cause all the operated relays in the link to be released. The cut-off relay therefore falls but the individual lock-out relay such as 50 is held by the immediate re-operation of the line relay over which the party-line now receives talking current. When both parties clear, the line relay falls and releases the lock-out relay. Selection of junction line. As before, the initiation of the call results in the operation of the subscriber's lock-out and cut-off relays, tens and units connecting relays in the link and also line and release relays 630, 620 and relays 680, 720, 710, 608, and when the first digit begins to come in, 660, 670, 400 are energized also. If the subscriber dials O, the relapse of 660 at the end of the digit makes circuits over front contacts of the counting relays 840, 860 for the tens relay 420 and for relay 613 which acts at a later stage as a back-bridge relay. A circuit involving contacts of 840, 860 and 420 is made also for the units relay 340. 613 energizes 360 and 700, and 340 connects the test lead of line 29 to the test relay 770 and completes a circuit for 350. If the junction is busy, 770 is short-circuited and in due course 350 tests the next junction. If this also i