Patent GB-753023-A (GB)
Title: Improvements in or relating to switching circuits for automatic telephone systems
IPC: H01H67/12
Filed: 1954-02-02
Abstract: 753,023. Automatic exchange systems. AUTOMATIC ELECTRIC LABORATORIES, Inc. Feb. 2, 1954 [March 9, 1953], No. 3075/54. Class 40 (4). Use is made of a rotary-radial switch such as is described in U.S.A. Specification 2,684,408 having a control magnet and a stepping magnet. When the control magnet is energized for the first time, impulses operate the stepping magnet to drive the wipers in a rotary direction. When the control magnet is subsequently restored, further impulses cause the stepping magnet to drive the wipers radially. Re-energization of the control magnet restores the wipers first in the radial then in the rotary direction. Local calls. Figs. 1-4 should be placed in order from left to right. Initiation of a call from substation 195 operates line relay R100 and hold relay R110 in known manner, the latter energizing series relay R145 and control magnet M200 in the first selector, Fig. 2. M200 prepares the selector for rotaty stepping and dial tone is returned over R145. The first impulse operates R140 so that line relay R100 repeats the first digit to stepping magnet M210 which drives the wipers 241-244 in a rotary direction, off-normal contacts 247 removing dialling tone. At the end of the digit R140 falls back to operate R160 in series with R150, the former restoring R145 and M200 to energize interrupter relay R185. Restoration of magnet M200 conditions the switch mechanically so that R185 and M210 co-operate to drive the wipers 241- 244 radially until they seize an idle intermediate selector, Fig. 3, when resistance battery on wiper 244 energizes switching relay R220. R220 connects the control circuit of Fig. 1 to the wipers, busies the intermediate selector, and restores R150, R160 to operate series relay R145 and control magnet M310. Ground through R120 operates release control relay R300, which remains energized until this ground is removed when hold relay R110 falls back at clear down. If all the intermediate selectors are busy the wipers are stepped to 11th position where off-normal contacts 229 open to prevent further stepping and contacts 249 open to restore R150, R160, the latter returning busy tone from conductor 218 to the calling line. Assuming that an idle intermediate selector has been seized, the second digit steps wipers 361-364 to hunt for and seize an idle connector, Fig. 4. Switching relay R330 then operates to restore R150, R160 so that series relay R145 and control magnet M400 operate. R145 reoperates R150, R160 as previously described and M400 operates ring cut-off relay R440. The third digit causes M410 to drive the wipers 401-404 in a rotary direction, after which change-over relay R140 restores to operate B150, R160 in series, the latter restoring R145 and M400, which then releases R150, R160. The connector is then ready to receive the fourth digit and only R100, R110, R220, R300, R330 and R440 are energized. In response to the first impulse R100 falls back and R140 operates as before, but now R170 pulls up. The fourth digit causes M410 to step the wipers radially, R100 reoperating and R140 falling back at the end of the digit. If the selected line is idle, release of R140 restores R170 so that switching relay R420 operates to battery on contact 468. R420 busies the selected line, completes a ring- ing circuit through the lower winding of R440, and operates R190 in series with R440, the resistance of R190 being so high that both R190 and R440 restore. While operated, however, R190 energizes R155, R150 and R130, R150 falling back with R190. R130 extends the talking circuit to contacts 442, 444 of the connector and removes the control circuits from both sides of the line. When the called party answers R440 reoperates, opens the ring- ing circuit, completes the talking circuit, and operates back-bridge relay R105 to supply battery for the calling line and reverse the connections of R100. If the called line had been busy, ground on contact 468 would have operated busy relay R180 through the lower winding of R420, which would not pull up, however, because of the high resistance of R180. R180 returns busy tone from conductor 139 and locks up when R170 releases after a short delay. Release. When the called party hangs up only back-bridge relay R105 restores. When the calling party hangs up the line circuit, line finder and R100 restore in known manner to energize R140 which operates R170 and releases hold relay R110. Release of R110 restores R130, R155, R220, R330, R420 and R300. R300 reoperates magnet M310 and R420 restores R440 which reoperates M400 to release -the switches of Figs. 3 and 4, respectively. R140 then falls back to reoperate M200 and release the first selector. P.B.X. For P.B.X. groups the terminals 467, 468 are connected on all but the last line so that if any but the last line is busy R180 operates as described, but when R140 restores interrupter relay R185 energizes from ground on terminal 467 to cause M410 to step the connector wipers radially to the next line. Inter-exchange calls. (1) Under conditions wherein the control unit of Fig. 1 replaces a repeater use is made of an inter-exchange control unit, Fig. 6, with a pulsing relay R600. Figs. 1, 2, 7, 6 and 2 again should be placed in order from left to right. The first digit connects the calling line to trunk lines 691, 692. As in a local call R160 restores but now R190 operates from battery over resistor 710 to hold R150 operated. Restoration of R160 operates R140 and pulsing relay R600 in series, the former operating R165. R600 energizes hold relay R615 which prepares a pulsing circuit and operates series relay R640 and control magnet M200 in the right hand Fig. 2. The call may then be completed under the control of R600 which follows R100. When a connection to an idle line is completed, switching relay 625 operates in the manner of R130. R625 restores R600, R140 and energizes R605. Release of R140 causes operation of R130 in series with R 155 as previously described to prepare the talking circuit and restore R190. The call is then completed as for a local call. (2) If an inter-exchange call is to be made over a trunk requiring a repeater, Fig. 7 is replaced by Fig. 7A. Connection is made to an idle trunk as before, R220 operating as before and R120 operating to resistance battery 700. R120 extends the calling line to R720 free of all control relays in Fig. 1 and at 128 prevents the reoperation of M200. R720 energizes R730 which busies the trunk. R120 also restores line relay R100 and busies the control unit at contacts 127b. The call is then routed to the distant exchange in known manner. Incoming toll calls. Figs. 8, 2, 3, 4 should be arranged in order from left to right. Incoming toll calls are routed by an operator over a toll board trunk selector, Fig. 8, in which the first three digits received by R800 control the first and intermediate selectors and the connector in the same manner as for local calls. At the end of the third digit R830 falls back and R850 operates in series with R840 to restore series relay R835 and control magnet M400. M400 restores R840, R850 and the ring cut-off relay R440 is held operated as for a local call. When the fourth digit is dialled, release of line relay R800 reoperates R830 to energize R860 and M410 steps the connector wipers radially to the selected contacts. If the called line is busy, operation of busy relay R870 and restoration of R830, R860 returns busy tone through coil 898 to the operator. If the line is idle, release of R860 operates switching relay R420 to operate R890 in series with R440. R890 then operates switching relay R820 which restores R890 and prepares the talking circuit while keeping R440 operated to withhold ringing current from the line. When the operator wishes to ring the line she operates R805 to restore R440. 200-line selector. The 100-line selector of Fig. 3 may be replaced by a 200-line selector, Fig. 9, comprising two sets of wipers moved simultaneously by stepping magnet M900. If both trunks seized are idle, preference is given to the upper wipers by a lock-out arrangement between the two switching relays R930, R940. 200-line connector with two sets of wipers. Fig. 10 should be placed to the right of Fig. 9. Operation is similar to that of the 100-line connector of Fig. 4 except that the connection depends on which of the two sets of incoming conductors is used. Control magnet M1000 operates in series with the series relay R145 of the control unit. The next two digits cause M1010 to move with both sets of wipers to the selected outlets but only the upper or lower switching relay B930 or R940 energizes according to whether the upper or lower set of incoming conductors is used. The call is then completed as for a 100-line connector. 200-line connector with one set of wipers. The bank contacts are arranged in 10 rows of 20 lines. If the connector is seized over the upper conductors 1161-1164 a first control magnet M1110 connects to one of the first 10 lines of one row as in the 100-line connector. If the connection is over the lower set of conductors 1165-1168 the first control magnet steps the wipers to a selected row of contacts. At the end of the first digit R140 restores and a second control magnet M1100 operates in series with R150, R160 to restore R145, M1110 whereupon interrupter relay R185 co-operates with stepping magnet M1120 to stop the wipers automatically to the tenth outlet in the predetermined row when off-normal contacts 1171 open to restore R160, R150 and prevent reoperation of R185. The second digit steps the wipers further in a radial direction, the end of the first impulse causing off-normal contacts 1169 to open to restore M1100. The connection is then completed as in Fig. 4. Party-line connector. Assume a call through Figs. 1, 2, 3, 12 in order from left to right. When the connector is seized control magnet M1240 operates in series with R145 and energizes R1230 which operates R1