Patent GB-762840-A (GB)
Title: Auto-selecting cross-bar telephone system
IPC: H04Q3/00
Filed: 1954-12-10
Abstract: 762,840. Automatic exchange systems. AUTOMATIC ELECTRIC LABORATORIES, Inc. Dec. 10, 1954 [Dec. 11, 1953], No. 35842/54. Class 40 (4). In a cross-bar exchange the seizure of a line circuit to initiate a call causes a start circuit to be extended via a winding of an outlet magnet of a cross-bar switch serving the group of lines which includes the calling line, and a free connecting circuit, the magnet operating in this start circuit and, together with the seized line circuit, causing operation of the relevant inlet magnet to extend a speech circuit from the line circuit to the connecting circuit. U.S.A. Specification 2,021,329 is referred to. General description. The operation of a call. ing subscriber's line relay brings up a hundreds relay common to the 100-line group which includes the calling line, which extends a start ground over a front contact of the line relay to the primary cross-bar switch serving the group of lines. This ground automatically finds a free path through the horizontal magnets of this primary switch, those of one of the secondary cross-bar switches, an idle connecting circuit, the horizontal magnets of the register finder cross-bar switch, and a free register, to battery in the common control circuit. The selected horizontal magnets operate in this circuit, and the register is seized. The vertical magnets appropriate to complete a connection from the calling line to the seized register are operated by the horizontal magnets, which are thereupon released. The register reverts dial tone and operates the caller's cut-off relay, whereupon the line relay and hundreds relay release, and another call may be dealt with. Local calls. The caller dials a three-digit number indicative of the wanted line, the first two digits of which are used by the pulse counting relays of the register to set a storage crossbar switch, the third digit'being momentarily stored by the counting relays themselves. The common control circuit thereupon disables the call initiating circuits momentarily, and the storage switch operates the tens relay appropriate to the first two digits, causes the operation of the cut-off relay of the wanted line (from the counting relays), and forwards a start ground to the primary switch serving the called group of lines. This ground finds a free path through the horizontal magnets of this primary switch and of a secondary switch connected to the local outward circuit of the held connector and thence via the register finder to battery in the register. The selected horizontal magnets in the primary and secondary switches operate in this circuit, the appropriate vertical magnets follow (that in the primary switch which is relevant to the called line being chosen by the operated counting relay), and a connection is extended from the connector to the called line, the horizontal magnets then being released. The connector releases the register finder, register and common control circuit, and proceeds to ring the called line, switching through when the called party answers. Outgoing calls. The caller dials the twodigit number assigned to the wanted trunk group, the storage cross-bar switch is set, and the trunk tens relay corresponding to the wanted trunk group is operated. An idle one of the associated repeaters is seized and forwards a start ground to the primary switch serving the group of trunks. A connection is then extended from the trunk outward circuit of the held connector to an idle trunk of the wanted group in the same manner as was the connection to a wanted local line. Incoming calls. These come in over a particular trunk to a particular repeater which then acts like a line circuit to cause the extension of the call. Detailed description (Fig. 1-10); Local call. When subscriber 191 takes down his receiver, line relay 110 pulls up in the loop and operates hundreds relay 140 to battery over a back contact of common control relay 805 and wire 803. Relay 140 disables the other hundreds relays and connects horizontal start ground over front 110 and back 115 (cut-off relay) to start wire 373, from whence it finds a free path to an idle connector and register. This path may be assumed to be via primary horizontal magnet 310A, wire 434, back contacts of vertical magnet 410 in the secondary switch, secondary horizontal magnet 410A, wire 504, back contacts of connector relays 510 and 520, back contact of vertical magnet 610 in the register finder switch, register finder horizontal magnet 610A, wire 901, register relay 915, back contact of release relay 920, and wire 801 to battery over back 805. The horizontal magnets 310A, 410A and 610A operate in this circuit and raise their selecting fingers; relay 915 also pulling up. The energized horizontal magnets disconnect the succeeding horizontal magnets, and operate the corresponding vertical magnets 310, 410 and 610, together with connector relay 526. Magnet 310 is chosen by the operated line relay 110. The cross-bar contacts 3131-3151, 4131-4151 and 6131-6191 are accordingly closed and the talking and test wires of the calling line are extended to the register. In the register the operation of relay 915 grounds the test and hold wires 905 and 909 and brings up pulsing relay 910, followed by release relay 920, whereupon 915 and the horizontal magnets are released. The vertical magnets 310, 410 and 610 lock up to register ground to which cut-off relay 115 operates, disconnecting line relay 110 which releases the hundreds relay 140. Relay 910 pulls up to the calling loop, slow-to-release release relay 920 follows, and dial tone is reverted from the register. The caller dials the number " 190 " of the wanted line, relay 910 repeating the impulses to the counting relays 1010-1000. Relay 1010 operates partially to the first impulse closing its X contact, the slow-to-release transfer relay 926 pulling up at the same time and releasing shortly after the reoperation of 910. The operation of 926 brings up slow-to-release relay 930 which applies ground over the X contact of 1010 to that relay. The re-operation of 910 at the end of the first impulse opens the original operating circuit of 1010 and that of 926; whereupon 1010 operates fully, locks up, and connects 1020 to the pulsing circuit in its stead, and 926 and 930 fall away in turn. During the interval between the release of the last two relays sequence relay 935 operates partially to close its X contact, and sequence relay 720 operates fully, bringing up the storage switch horizontal magnet 710A over wire A of cable 760. The relapse of relay 930 releases 720 and 1010 and allows 935 to operate fully, thus disconnecting dial tone. The reception of the second digit "9 " results in the operation of counting relay 1090, and, when 926 again restores, sequence relay 940 operates partially to close its X contact, and storage-connect relay 730 operates fully to operate storage switch vertical magnet 790, whereupon cross-bar contacts 19, 99 and 09 are closed. The relapse of 930 releases 730 and 1090, and causes sequence relay 940 to operate fully, thus disconnecting the storage-connect relays and releasing sequence relay 935. The third digit " 0 " results in the operation of counting relay 1000, and on the release of 926 sequence relay 950 operates fully to hold relay 1000 after 930 relapses. Relay 950 also releases 940, opens the pulsing circuit, and brings up the common control relay 810 individual to the register over wire 841. Relay 810 operates trigger relay 970, disconnects the succeeding common control relays, and brings up the power control common control relay 805, which momentarily disables the call initiating circuits by disconnecting the vertical magnet start ground from the primary switches, and battery from the other common control relays, the relays 915, and the hundreds relays. Trigger relay 970 closes a circuit for busy relay 985, which being slow-to-operate is not immediately actuated, and also brings up tens relay 130 over wire 773, storage cross-bar contacts 19, and wire 185. Relay 130 grounds the horizontal start wire 373, and, providing the called line is idle, operates the cut-off relay 125 in series with the register idle test relay 980. Cut-off relay 130 disconnects line relay 120, and idle test relay 980 disconnects busy relay 985 before it can be operated. The ground on wire 373 finds a path through primary switch horizontal magnet 320A, back contact of secondary switch vertical magnet 420, secondary switch horizontal magnet 400A, upper winding of local-switching relay 550, register finder contacts 6181 and 6171 to battery via the upper winding of local-switching relay 520. The horizontal magnets and relays 520 and 550 all operate. Vertical magnets 300 and 420 follow, cross-bar contacts 3032, 3042, 3052, 4230, 4240 and 4250 are closed, and horizontal magnets 320A and 400A are released, vertical magnet 300 being chosen by the operated counting relay 1000. In the connector, relay 520 extends the calling loop to operate batteryfeed relay 530 and disconnects register relay 910 to initiate release of the register. Relay 550 completes the ringing and ringing-tone circuits, locks to ground at front 530, and extends this ground to hold the called side of the connection and to shunt relay 980 which commences to release. In the register the release of pulsing relay 910 brings down release relay 920, whereupon the register finder vertical magnet 610, the sequence and counting relays 950 and 1000, and the vertical and horizontal magnets 790 and 710A of the storage switch are released. Relay 1000 disconnects test relay 980 to complete its release, the storage switch releases the tens relay 130, and relay 950 releases the common control relay 810, which in turn releases relays 805 and 970 to restore the register to normal and make it available for use in another call. The called line is rung from the connector, ring-trip relay 545 operating on the reply of