Patent GB-576834-A (GB)
Title: Improvements in or relating to switching systems and apparatus
IPC: H01H67/26
Filed: 1943-07-02
Abstract: 576,834. Automatic exchange systems. STEVENS, A. H. (Kellogg Switchboard & Supply Co.). July 2, 1943, No. 10793. [Class 40 (iv)] In a cross-bar exchange, each hundreds division comprises a group, e.g. 2LP, 4LP, of line primary cross-bar switches and a group, e.g. 2LS, 4LS of line secondary cross-bar switches which act under the control of common equipment, e.g. 2LCE, 4LCE, to extend a calling line to the group selecting stage and to extend a trunk from the group selecting stage to a wanted line. The cross-bar switches in different groups differ in size in accordance with traffic requirements and all those in the group use a common set of select magnets. The group selecting stage comprises up to ten groups, e.g. 2SP, 4SP of primary cross-bar switches, one for each of the hundreds divisions in use, and corresponding groups 2SS, 4SS of secondary switches and common control circuits 2SCE, 4SCE. The number of primarysecondary links (and consequently the size and number of the switches) depends on traffic requirements and differs in different groups. Each trunk incoming to the primary switches of the group selector stage has an individual (hundreds) register and each trunk outgoing from the secondary switch of the stage comprises a feed circuit and a tens and units and if necessary a party-line digit register. Each group of switches forming a group selector stage has a common set of select magnets. The outgoing trunks from the group selector secondary switches are connected to the line secondary switches by additional distributer cross-bar switches, e.g. 2D, 4D. The switches described have detachable horizontal units, each comprising sets of relay springs and a pulldown magnet, the set to be operated being selected by a set of select magnets common to a number of horizontal units and arranged to move a finger mounted on the horizontal unit between a spring set and the armature of the pull-down magnet. Specification 555,638 is referred to. Construction of cross-bar switches. These are built up from a number, which depends on the function of the switch, of separately attached horizontal units, each comprising a horizontal operating magnet 34 and five pairs of spring sets of which the movable contacts are formed integrally with multipling strips provided with inlet terminals 70 &c. The vertical select-magnets M1 ... M10 rock bars provided with blades 23 which lie between pairs of pivoted members 26 held together by a light hairpin spring and embracing projection 28 on the tails of selecting members 30 associated with each pair of spring sets. A selecting member 30 is capable of limited movement in either direction to bring one of two projections 31 between one of the associated spring sets of a pair and a common operating bar controlled by the horizontal magnet. The selecting member 30 is latched by the operation of the horizontal magnet and the vertical bar can thus be restored to normal, separating the members 26 of the operated set but producing no effect on the springs themselves. The movable springs are adapted for straight bare wire multipling by lateral projections. Each vertical bar also actuates a set of contacts when it is rocked in either direction. The operating mgnets of more than one column of units can be interconnected so that the whole acts as a single switch. Non-numerical operation of double-purpose line primary and secondary switches. Each 100-line group has a group of ten primary switches, e.g. 2LP, 4LP, &c. (Figs. 10A, Pt. 1, 18 and 31), each switch having ten inlets and a number of links depending on traffic requirements (6 in 2LP and 4 in 4LP) with a group of secondary switches 2LS, 4LS, &c. (Figs. 10A, Pt. 2, 19 and 32). Each of the links from any one primary switch goes to the same position in a different one of the secondary switches. The secondary switches have outgoing links to first selectors and incoming links from distributers in accordance with traffic requirements. The switches of a group share a set of ten select magnets. When a subscriber calls, his line relay 1802 operates a tens relay 1621 ... 1630 in series with an auxiliary tens relay 1611 ... 1620 in a control circuit LCE individual to his hundreds group and applies a marking potential to a wire such as M11 individual to the line. The operated relay energizes 1502. The tens relays are arranged in a chain so that only one can remain operated at a time and energize the respective select magnets M1 ... M0 in the corresponding group of secondary switches such as 2LS, and the auxiliary relay connects the ten marking wires from the calling tens group to ten units relays 1721 ... 1730. These are arranged in a chain circuit so that only the lowest of several relays operated can remain energized. This relay operates the corresponding select magnet M1 ... M0 in the group of primary switches such as 2LP. The auxiliary relay also connects test relays 1403 ... 1408 to the wires H of the six links running between the calling primary switch and the secondary switches. Battery on the H wires of such of the links as are idle, provided the corresponding secondary switches have outlets, energizes the corressponding test relays partially, but only one is able to lock-up, the others being cut off by 1402 which operates in the locking circuit. The locked test relay determines which of the secondary switches of group 2LS is to be used and connects test relays 1411 ... 1414 to the H wires of this switch. The relays corresponding to idle outlets pull up, but only one can lock up, the others being cut off by 1415 which is energized in the locking circuit. This relay energizes a sluggish relay 1507 which energizes 1506 which pulls up sluggishly, locks and cuts off 1507. While the latter is operated, control of the tens and units relays is prevented and an operating ground is connected via 1533 to the pull-down magnets corresponding to the outlets from the primary and secondary switches selected respectively by the test groups 1403 ... 1408 and 1411 ... 1414. These magnets operate over low resistance windings and are then held, from the selector, over high resistance windings. Cut-off relay 1803 is energized over wire S from the selector and the relapse of line relay 1802 removes the marking potentials from the control equipment LCE, whereupon the units relay 1721 ... 1730 falls. The re-operation of one of these relays by another call is deferred until after the relapse of 1507 has restored the operated tens relay and auxiliary relay. 1502 now falls, releasing the primary and secondary test and cut-off relays 1403, 1402, 1411, 1415. Finally, 1506 falls to enable the equipment to be used again. Group selecting stage. The links SL from the line secondary switches have individual registers for the hundreds digit and are connected to selector multiples SM connected in groups of ten to a number of selector primary cross-bar switches, one for each possible hundreds digit. The switches corresponding to a particular digit are assembled in a single group SP with a common set of select magnets. Each group of selector primary switches, e.g. 4SP gives access to a group of selector secondary switches, e.g. 4SS, there being as many switches in a secondary group as there are outlets from one primary switch and each such outlet appearing in the same position in a different secondary switch. A common control circuit, e.g. 4SCE, is provided for each primary/secondary group. Each link SL has an individual hundreds register of relay type. When the calling line has been extended to a link SL, the associated register line and hold relays 1102, 1103 pull up and the latter energizes cut off relay 1803. The hundreds digit is repeated to dialling relay 1105 and with the aid of a relay 1106 to a counting chain 1107 ... 1112. The chain is such that the first impulse energizes 1107 which locks in series with 1106 which is unable to operate until the end of the impulse. The next impulse energizes 1108 and releases 1107 and at its end, 1106 falls again. The chain builds up in this fashion to 1112 which is operated by the sixth impulse and remains operated while the remaining impulses build up the chain from 1107 again. The chain controls the application of ground to two sets of ten wires SC1, MC1 which are taken to crossconnecting frames, Fig. 13, by means of which they are connected with those from other registers to the various common control equipments such as 4SCE. These wires are led into the common equipment via pairs of blocks 3611, 3612 and 3613, 3614 which allow for various cross-connections. As shown, the wires SC from the register are connected together in groups of ten corresponding to the groups of ten links SL which lead to a particular set of cross-bar switches. When the dialling relay 1105 falls back, ground is connected to the selected wire SC and this operates a relay in the group 3701 ... 3712 corresponding to the group of ten links SL comprising the calling link in the selected common equipment, say 4SCE in series with a relay 3805. The operation of this relay connects the individual wires MC from the group of links to relays 3601 ... 3610 and that corresponding to the calling links operates. Both these relay groups are arranged so that only one relay of the group can remain energized at a time. The relay 3701 ... 3712 operates the select magnet in the associated group of secondary switches which corresponds to the calling group of links SL and the relay in the group 3601 ... 3610 corresponding to the particular link SL that is calling operates in series with the corresponding select magnet M1 ... M10 in the associated group of primary switches. The relay 3701 ... 3712 also connects test relays 3901 ... 3904 over offnormal contacts to the respective pull-down magnets of the selector primary switch accessible to the calling link the circuits only being completed if the secondary switch reached over a particular