Patent GB-530585-A (GB)
Title: Improvements in or relating to telephone systems
IPC: H04Q3/58
Filed: 1939-06-13
Abstract: 530,585. Automatic exchange systems. MERCER, R. (Associated Electric Laboratories, Inc.). June 13, 1939, No. 17330. [A Specification was laid open to inspection under Sect. 91 of the Acts, March 9, 1940.] [Class 40 (iv)] A calling subscriber at an R.C.X.D. is extended non-numerically to a control relay group CG-1 at an exchange A, the relay group being accessible also to other exchanges (not shown) and having associated with it a numerical switch IC-1 not used for local calls in exchange A, and thence by a further non-numerical stage to a control operator at an exchange B who can set the switch IC-1 to a group of junctions to one of the other exchanges. In the system shown, an R.C.X. is controlled over two or more junctions in tandem with intervening repeating coils, control being exercised over the first function in a loop circuit and over subsequent junctions in simple X circuits. Both circuits involve differential relays which operate when the circuits are unbalanced to control inter alia the application of ringing current. Means are provided for storing for a limited time calls which have not been answered. Apparatus otherwise left off-normal is forcibly released. In the detailed description the first digit of four-digit reference numbers and the first two digits of five-digit reference numbers indicate the figures in which the circuit elements concerned are to be found. The penultimate digits show the relative positions of the circuit elements from left to right in the figure. General arrangement. The network shown in Fig. 1 comprises a control centre B having twoway junctions TWTÀ1 to a small automatic tandem exchange A like that described in U.S.A. Specification 1,999,788. A two-way junction TWTÀ2 runs to a magneto manual exchange C and further two-way junctions such as TWTÀ3 run to sub-tandem exchanges such as D. The latter and their satellites such as E are of the R.C.X. type and calls to them from A and C are set up with the help of the control operator over an incoming connector such as IGÀ1 the two-way junction TWTÀ1 being released or retained at the will of the operator. Calls are initiated at the sub-tandem exchange D and its satellite E by operating the magneto and the connections are extended via the finder portions of local links, non-numerical switches TSÀ3 TSÀ1 associated with inter-exchange junctions and non-numerical switch TS.2 by means of which an idle control circuit is taken into use. Calls originated on R.C.X.s are cleared by ringing off or by the action of timing equipment, the exchange E using for this purpose timing equipment at D. Incoming calls are set up in R.C.X.s over the connectors of ordinary links. Prepayment stations are identified to the control operator by a special tone. Faults arising in A cause an alarm to be operated at B and the operator can ascertain the relative seriousness of the fault by dialling a special test number. Means are provided for modifying the order of choice of the first two of certain pieces of apparatus, e.g. junction circuits, so that successive calls finding all junctions idle employ the first two junctions in turn. Local calls in tandem automatic exchange A. When subscriber TÀ1, Fig. 2, calls, his line relay 2510 energizes start relay 5510 which is followed by 5520, 5570, 5550 in the allotted circuit and 2590 and finder vertical magnet 2550 in the pre-selected link. 2550 interacts with stepping relay 5540 until vertical wiper 2908 encounters the marking ground applied by the line relay whereupon 5530 pulls up in series with 5540, locks and opens its original circuit. 5540 then interacts with the rotary magnet 2560 until the calling line is encountered whereupon switching relay 2580 pulls up quickly in series with cut-off relay 2520 which is shunted by a resistance at this stage. 2580 locks and applies full ground to the test-wiper to operate 2520. In the link circuit, line and release relays 3530, 3540 pull up and also change-over relay 3560 which sends back dialling tone. On the operation of 2580; the allotter, Fig. 5, is driven on by self-interruption until wiper 5908 finds a blank terminal. Vertical and rotary magnets 3570, 4570 set the switch in response to two digits in known manner. Relays 4530, 4540 are energized, parallel with the rotary magnet and the former is locked by the latter which is sluggish. If the line is busy, 4550 pulls up over the test wiper before 4530 can fall, locks itself and sends back busy tone. If the line is idle the relapse of 4530 energizes 4560 in series with the cut-off relay of the wanted line, and the line is rung in the usual way. When the called party replies ring trip relay 4520 pulls up in two steps and completes the talking circuit whereupon back bridge relay 4510 energizes 3520 to reverse the direction of the calling side feed. Complete release of the link is under control of the calling party. Call from exchange A to magneto exchange C. The connector seizes ,and rings the junction line in the same way as a local line. Cut-off relay 10520 pulls up in the junction circuit at A and, in response to ringing current, 9500 at C energizes 9520 which lights lamp 9909. When the operator plugs in to J2, 9530 unlocks 9520 and polarizes 9540 and bridges it across the junction. 9540 pulls up over the junction, since magneto junctions have their speech wires reversed in the connector bank, and extinguishes the lamp. When the calling party clears, the normal direction of current is restored by the release of the connectors and cut-off relay and the lamp glows again. Relay 9510, which shunts the calling relay when the operator replies, maintains the shunt for an interval after she clears. Complete release of the link is under control of the calling party. Call from exchange A to control centre B. When a connector is stepped to the tenth level springs 4902 energize 4510 which energizes 4550 before 3560 can fall and the rotary magnet 4570 then interacts with 4550 until wiper 4908 finds an ungrounded terminal and 4550 is thus unable to pull up. Switching relay 4560 pulls up over the test wiper and a resistance such as 16900 in the idle control group circuit. 4510 is released and 3510 extends a clean metallic circuit from the line to the talking wipers and energize 16520 in the trunk circuit. Relays 3530, 3540 fall but relays 3510, 4560 are held by ground returned from the control group by its elease relay 16530 which also energizes 16540, 5590 and 20540. 18560 and 19570 are ener- ;ized by 16540. 19570 reverses the battery onnections to the talking wires 20000, 20001. 20540 grounds the start wire 20003, puts a narking ground on wire 20002 and energizes 21590 which operates and locks, and also 21530 in the allotted junction switch which is hen driven in search of the calling control circuit by interaction of magnet 21500 with 21510. When wiper 21903 finds the marking ;round, 21510, 21520 stop the switch and switch hrough. 21520 locks in series with 19580 and extends the starting circuit releasing 21530. telay 20560 which was connected up by 20540 nergizes 20550, if or when ringing current is vailable over lead 7008, and starts a burst of inging current over the junction and brings down 20570. Relay 19580 releases 20540, nergizes 20580 and connects up the ring back tone lead. Relay 20560, when 20540 and 20570 ave both dropped, terminates the burst of ringing current and releases 20550, whereupon 0570 pulls up again. Relays 23560, in response to the burst of ringing current, locks mechanically and lights lamp L-23-1. When the operator lugs in sleeve relay 23570 releases and disonnects 23560, energizes 23550 and bridges the junction by polarizing supervisory relay 23540 to complete a circuit for 19530 (which is marginal), 19540 and 19560 (which is differenial) at exchange A. 19530 and 19540 pull up and then 18580 which replaces the holding ground n the c wire to the connector by ground through transformer 20510 (lower), gives control of release of the switch train to the operator y making this connection independent of release relay 16530, and energizes 18570 which removes ng-back tone and makes a new circuit for 19580 to give control of release of TSÀ1 to the perator. Since 19570 is energized, the direction E current in the junction is such as to energize 3540 and this is followed by 23580 which isconnects battery and ground from the cord circuit talking wires to give a signal. Release of connection from A through B. Then the calling party hangs up 16530, 16530, 15590, 20580, 16540, 18560, 19570, 1660, fall back and on the restoration of the normal direction to the current in the junction 23540, 23580 fall back to give the clearing signal. When the plug is withdrawn the sleeve relay replaces the existing direct current circuit over the junction by one through a high resistance relay 23600 whereupon 19530, 19540, 18580 fall back and releasing relay 18550 pulls up energizing 16570. On the relapse of 18580 the switch train is released and 18570, 19580, 21520, 18550 and 16570 fall. The equipment is now in normal condition. If the calling party does not clear the operator releases the circuit in a similar way and the subscriber is locked out. Calls from magneto exchange C. The operator inserts the plug of a cord circuit (not shown) into J2 and the dialling plug P into J1 and operates K3 momentarily. 9530 locks, lights lamp 9909, polarizes 9540, energizes 9510 and loops the line. At exchange A line relay 10510 pulls up and a link circuit is associated and controlled as in a locally originated call. The operator then withdraws plug P to complete the talking circuit and connect up the supervisory relay 9540 which does not pull up to extinguish 9909 until the distant subscriber's reply reverses the connections of connector line relay 3530. When the called party clears, the connections of 3520 are restored to normal and the lamp 9909 is lit. In calls to the control centre the magneto operator after passing the me