Patent GB-636920-A (GB)
Title: Improvements in or relating to automatic telephone systems
IPC: H04Q3/00
Filed: 1947-08-07
Abstract: 636,920. Automatic exchange systems. WESTERN ELECTRIC CO., Inc. Aug. 7, 1947, No. 21768. Convention date, Nov. 16, 1938. [Class 40 (iv)] In an automatic exchange, means are provided which enable the directory number used in routing calls to a subscriber's line to be altered without altering the connections between the line terminals and the switch terminals at the exchange. The system disclosed is a marker-controlled cross-bar system in which the subscribers' lines are connected to primary line switches each having ten outlets. One to seven primary line switches are arranged in a horizontal group to form one level, ten levels form a frame, and four frames constitute one line choice. In the following description, the first digit of a three-digit reference numeral indicates the number of the figure in which the corresponding part is shown. Registration of called number and connection of marker to number-group frame. A call originated by a subscriber at sub-station 100 is extended to an incoming junctor 101 which connects with an idle terminating sender 103 through a link 102. The sender receives the number of the wanted party and transfers it to a terminating marker where the digits are stored on relay registers represented by the thousands, hundreds, tens and units relays 300 to 303 respectively. The hundreds relay 301 operates relay 305 for digits greater than 5 and indicates the position of the digit in the series 1 to 5, or 6 to 0 by operating one of five relays such as 304. The thousands relay 300 marks one of ten conductors (e.g. 306) which is extended to one of two relays (e.g. 307, or 308) according as 305 is back or up. Relays 300 and 301 thus identify a 500-number group by operating one of twenty relays such as 307. The tens relay 302 operates relay 310 for odd digits and identifies a block of twenty numbers by operating one of five relays (e.g. 309) which is followed by relay 311. The units relay 303 grounds one of ten conductors which are extended to one or other of two further groups of ten conductors according as 310 is up or back. The joint operation of 304 and 307 selects a number-group frame by operating a markerpreference relay (e.g. 105 of frame 107) as soon as the frame is idle. Relay 108 then pulls up and a hundred-block relay 109 and a twentyblock relay 110 follow under control of relays 304, 308 and 311. Three circuits for each of the twenty numbers in the twenty-block selected are extended from the marker to twenty sets of three terminals (e.g. set 111 to 113) on the number frame 107. On the number frame there is provided a first block of control terminal strips L representing line switch levels and comprising forty strips, one for each level of the four frames in a choice. A second block of terminal strips C combines identification of the line choice and the class of line, there being 10 sets (1 per choice) each of three strips. The first strip of each set represents an individual line, the ring party of a party line, or the last line of a PBX group; the second strip, the tip party of a party line; and the third strip, the first or an intermediate line of a PBX group. The second terminal of each set of 3 number terminals is jumpered to the strip of the first block which corresponds to the level in which the line of the party associated with the number is connected; and the third terminal is jumpered to that set in the second block which corresponds to the line choice which includes the party's line and to that strip in the set which corresponds to the class of the line. The first number terminal of each set is wired directly to the winding of the hold magnet of the line associated with the number and thus to the P-wire of the line concerned. The first number terminal of each of the twenty sets which are extended to the marker is connected to one of twenty busy-test relays (e.g. 111 is extended to 312); the second terminal to an armature of one of 20 selecting relays (112 to armature of 314) ; and the third to one of 20 relays which are effective only when PBX-hunting is required (113 to 316). Signalling location of wanted line to marker. The marker requires to know the line choice, frame and level in which the called line is situated and the class of service to which it is entitled. This information is contained in the markings applied to the first and second terminals of the set of number terminals of the called line. Ten choice relays 400, 401 ... are provided, each having three windings, so that the winding over which a choice relay is operated may indicate the class of service. To indicate the frame and level, twenty doublewound relays 402 ... , 405 ... are provided. These are arranged in pairs, each pair corresponding to a level. Each relay in a pair corresponds to a pair of frames and each winding of a relay to one frame of the pair. Thirty conductors from the windings of the choice relays and forty from those of the frame/level relays are extended in multiple to contacts of all the number - frame connector relays 108 ... 131 and thence to the sets of terminal strips on the number-group frame, e.g. conductors 406 to 408 of choice relay 400 extend to strips 117 to 119, and conductors- 409 to 412 of frame/level relays 402 and 403 extend to strips 120 to 123. The subscriber's line 200, assumed to be the wanted line, is connected to a distributing frame 201 from which it is extended to the primary line switch 202 at line terminals 203, 204 with private terminal 205 and metering terminal 206 individual to the line. The set of number terminals corresponding to the number 200 is 111 to 113. The terminal 111 is jumpered direct to terminal 205, and as line 200 is on No. 0 level of No. 0 frame in No. 0 choice and is an individual line, 112 and 113 are jumpered to strips 120 and 117 respectively. On the operation of twentyblock relay 110, the P-wire of line 200 is extended to busy-test relay 312 which operates if the line is busy. Relay 316 and the lefthand winding of choice relay 400 are then connected in a series circuit including opposed batteries and do not operate. After an interval to permit operation of the busy-test relay ground is connected, under control of the units register 303, to conductor 318 and if the called line is idle (312 back) relay 314 pulls up, and grounds conductors 319 and 320. The ground on 320 first operates choice relay 400 over its left-hand winding indicating No. 0 choice, and is then extended by 400 to bring up 413 indicating an individual line. The ground on 319 first brings up frame/level relay 402 over its left-hand winding (No. 0 level), and is thereby extended to operate 414 (No. 0 frame). Marking of wanted line. With relay 400 up the No. 0 line choice is selected by operation of marker-preference relay 207 (individual to the marker) followed by 208 which extends all the control circuits to the choice. Relay 414 closes a circuit over the winding of 418 to relay 209 (individual to the No. 0 frame) over equipment (not shown) which determines whether the frame equipment is idle. If the frame equipment is idle 418 operates and grounds the outer left-hand contacts of the frame/level relays 402, 404 ... Relay 402 being up, horizontal level relay 210 operates to this ground and connects the operating circuits for the ten select magnets corresponding to the ten line junctors serving the wanted line through to the marker which selects one as part of a channel in substantially the manner described in Specification 466,986. The hold magnet 211 of the wanted line is operated by relay 314 after an idle channel has been selected. Wanted number denotes the tip party of a two-party line. Terminal 113 is jumpered to strip 118, so that relay 400 is operated over its middle winding and is followed by relay 419 which controls the ringing and charging functions of the marker. Wanted number denotes PBX line other than the last of a group. Terminal 113 is jumpered to strip 119, and thence to conductor 408. Prior to the operation of selecting relay 314, relays 420 and 421 and similar relays associated with the other choice relays are operated and ground is applied to the righthand operating conductors of all the line choice relays. Relay 316 and all similar relays in the same PBX group are operated so that the first idle trunk of the group may be selected in substantially the manner described in Specification 466,986. When this idle trunk is found and the selecting relay comes up, relays 420, 421 ... fall away and close an operating circuit for the line choice relay over its right-hand winding. Operation of the choice relay is followed by that of relay 423 which indicates that the line is one of a PBX group. Change of directory number. If the number assigned to line 200 is to be changed, say to that individual to number terminals 114 to 116, the jumpers running to terminals 111 to 113 are diverted to terminals 114 to 116, no other change being necessary. Change of line location without change of number. Assume it is desired to move the line 200 to the No. 9 level of No. 2 frame of No. 9 choice. The line conductors are disconnected from terminals 203, 204 and transferred to terminals 212, 213 at the new location; the jumper running from terminal 111 is transferred from terminal 205 to terminal 214; and the wire from the subscriber's meter is transferred from terminal 206 to terminal 215. At the number frame the jumper from terminal 112 is transferred from strip 120 to strip 129, and that from terminal 113 from strip 117 to strip 130. The No. 9 line choice relay 401 and the frame/level relay 405 are then operated over their left-hand windings, consequent upon the registration by the marker of the number 200, and the marker is directed to the new line location. This feature allows the lines of busy PBX groups to be spread over all the line choices, thus relieving the load on any one choice. Specification 530,085 and U.S.A. Specificati