Patent GB-234059-A (GB)
Title: Improvements in or relating to telephone systems
IPC: H04Q3/42
Filed: 1925-03-17
Abstract: 234,059. Automatic Telephone Manufacturing Co., Ltd., (Assignees of Stehlik, R. F.). May 19, 1924, [Convention date]. Automatic exchange systems.-Two co-ordinate call-finders F, Fig. 1, having two sets of wipers and therefore access to 200 lines, are set on to a calling line by numerical impulses transmitted from a sending switch, Fig. 4, the number of impulses generated being determined by a set of common line relays, Fig. 3, of which the tens relays 201 - - 210 are common to the whole 200- line group whilst there are two sets of units relays 211 - - 220, 221 - - 230, common respectively to the first and second hundreds of the group. The circuits are such that, in order to prevent wrong connections due to two or more lines simultaneously calling, only a tens relay operates at first and in operating cuts out all other tens relays and effects circuit changes so that the units relays can then operate, the circuits of the latter also being such that not more than one relay can remain operated at the same time. The earth potential for the stepping magnet of the sending switch is picked up by the controlling wiper 301, 302 or 303 so that the switch continues to operate at a rapid rate until the wiper reaches a terminal which has been marked by the removal of earth. The finders F are arranged with their wipers normally opposite the first level so that if the calling line is in the level, rotary motion only takes place. Each finder switch is associated over a distributing frame IDF<1> with a hunting switch SS, Fig. 2, the next idle link comprising switches F, SS, being assigned by allotters FA1, FA2 which 'both serve the same. group of links and are employed alternately, the allotters also serving to control the connection of the common sending-mechanism, Fig. 4, to the, particular finder F in use. Provision is made whereby, if the test wiper, 17 or 20, engages an earthed terminal due to the calling line having been seized for an incoming call whilst the finder was operating or due to faulty setting on a busy line the switching relay 24 of the finder is not operated and the connection is released. The calling lines are connected to the finder bank over a distributing frame IDF so that the grouping of the lines in the banks of the finders may be altered at will without any renumbering or regrouping of the lines as regards incoming calls. Special arrangements are provided for mounting the cut-off relays 4 adjacent to common horizontal and vertical bars which serve for the multiple connections to the common line. relays. Certain features described in the parent Specification are claimed in a divided Specification 253,761. Initiation of call; operation of recording-relays, Fig. 3. When subscriber A (No. 33 in the first hundred) removes his receiver, the third tens relay 203 operates over the circuit 310, 241, 235, 7, 2, 3, 11, 8, 246, locks up, connects battery over coil 280 to the third common lead 233, and removes earth from conductor 273 in the bank of wiper 301 of the sending switch. Relay 234 in the locking circuit of relay 203 disconnects all the tens relays from the common leads and operates relays 244, 254 to remove short-circuits from all the units relays so that the third units relay 213 in the first hundred now operates over the calling line and coil 280, locks up, and removes earth from conductor 283 in the bank of wiper 302. Relay 249, in the locking circuit of relay 213, operates relay 257 and these two relays disconnect all the units relays from the common leads and complete a starting circuit over lead 263 for the sending-mechanism. Control and operation of finder F. Relay 321 energizing in the starting circuit 263 completes a circuit 362, 384, 69, for relay 26 which connects the allotted finder F to the common controlling leads 61 - - 67. Relay 321 also closes a circuit 360, 211, 348, 303 for the upper winding of relay 314 which partially operates two-step relay 316 to close armature 340 and connects up fast interrupter 307 to stepping magnet 305. At the succeeding de-energization of magnet 305, wipers 301 - - 304 move one step, relay 315 operates over wiper 304, relay 314 remains locked to earth on wiper 301 and this earth is also connected to the synchronous interrupter 307, 308. At each " make " of these interrupters an impulse is sent over interrupter 307 to magnet 305 and over interrupter 308 and lead 61 to the vertical magnet 31 of the finder F. After two impulses, by which the finder is raised from its first to its third level, wiper 301 engages the non-earthed lead 273, relay 314 releases to disconnect the interrupters, a restoring circuit over springs 306 and wiper 304 is completed for the sending switch, and relay 316 operates fully over both its windings. The transmission of the second digit now takes place in a similar manner under the control of wiper 302, three impulses from interrupter 308 being transmitted over lead 62 to the rotary magnet 30, after which a second two-step relay 317 operates completely. A call from a subscriber A' in the second hundred is extended in a similar manner, with the addition that each of the units relays 221 - - 230 connects earth over conductors 262, 65 to operate wiper-switching relay 23. In a call from a subscriber on the first level, the first tens relay 201 connects earth over lead 271 to operate relay 316 at once so that wiper 302 and conductor 62 are connected up and a single set of impulses is transmitted to the rotary magnet 30. Operation of hunting switch SS. Relay 321 in the starting circuit also connects the lower winding of the common test relay 322 over lead 67 in series with stepping magnet 101 of switch SS and interrupter 102, whilst a point in this circuit between relay 322 and magnet 101 is connected over lead 64 to test wiper 104. Hunting thus takes place until a free first group selector S is found when relay 322 operates. The line relay 111 of selector S energizes over the upper line conductor 161 and lead 66, and release relay 112 also operates and earths the test lead 55, 162. Completion of connection to selector S; release of line relays, Fig. 3. When both switches F, SS have completed their operations, relays 317, 322 complete a circuit over wiper 383 for switching relay 24 which operates the cut-off relay 4. The battery connection to lead 241 is now opened so that relays 203, 234, 244, 254, 213, 249, 257 are released and another call can be dealt with. Relay 321 releases, disconnects relay 26 which at its armature 46 marks the finder F busy to the allotter FA1, and releases relays 322, 316, 317. Relay 385 now operates over its lower winding and contacts 344, 356, 383, 46 to disconnect allotter FA1 and de-energize relay 390 which connects up allotter FA2 for the next call. At the same time stepping magnet 381 of allotter FA1 which was energized by the operation of relay 322 is released and advances wipers 383, 384 one step. If the terminal now engaged by wiper 383 is busy, magnet 381 operates again and hunting continues until an idle finder is found. Release. When the calling subscriber hangs up at the end of conversation, the removal of earth from lead 162 by a succeeding switch releases relays 4, 24, the latter closing a circuit 142, 57, 40, 28 for release magnet 29. False call due to faulty line. If an accidental earth occurs on subscriber's line 2, tens relav 203 will operate and relay 234 will earth lead 240 and operate in succession slowto-energize relays 325, 324. Since no circuit is in this case completed for relay 321, the operation of relay 324 sounds an alarm buzzer 309 and opens the battery connection to relays 203, 234 which release. If the earth on line 2 persists, the cycle of operations will be repeated and buzzer 309 will sound intermittently. An accidental earth on the line 3 does not produce any immediate effect and is prevented from permanently short-circuiting the units relay 213 and so interfering with a call from another line having the same units digit by the resistance 11. Defective switches. If a finder F is faulty, relay 4 is not operated, the tens and units relays 203, 213, remain locked up and the next allotted finder is set in operation to find the calling line. If the switch SS is faulty so that relay 322 is unable to energize, the circuit for advancing allotter FA1 is completed at armature 369 after an interval caused by the successive de-energization of slow-release relays 325 - - 323 after the circuit of relay 325 has been broken by relay 315, and the allotter is thus not permanently tied to the defective link. An attendant may temporarily put a finder F out of action by removing the pin which connects springs 50, 51 and inserting it to connect springs 51, 52, thereby marking the finder busy. A similar arrangement is provided for the selector S. Busy line engaged by finder F. If, for any reason, the test wiper 17 or 20 finds an earthed test terminal, this earth is extended over armature 34, 39 to short-circuit switching relay 24 and so prevent interference with the busy line, the finder F being released. All selectors accessible to switch SS busy. A relay 141 is normally short-circuited over parallel circuits 143, 117, 129, 107 of all idle selectors S. If all selectors are busy, relay 141 energizes and grounds conductor 68 to mark the link circuit busy to allotter FA1. All finders busy. A relay 319 is normally shortcircuited over lead 63 and parallel connections 28, 40, 51, 142 of all idle link circuits accessible to allotter FA1. If these are all busy, relay 319 energizes to disconnect stepping magnet 381. If both allotters are standing on busy finders owing to all finders accessible to both allotters being busy or to both switches simultaneously hunting, a shunt-field relay 318 is energized over both its windings and wipers 383, 397. to open the starting circuit for relay 321 and to disconnect battery from lead 241. Selectors and associated swit