Patent GB-191215952-A (GB)
Title: Telephone Machine Switching System.
Filed: 1912-07-08
Granted: 1913-07-08
Abstract: 15,952. Western Electric Co., [Western Electric Co.]. July 8. Automatic and semi - automatic exchange systems.-A system is described in which a calling subscriber is connected by first and second line-finding switches to an idle firstselector trunk, and thence by a lateral connexion through a distributing-switch to an operator, who enquires the wanted number and writes it down on a key-set, the connexion being then completed automatically through numerical selectors. The connexion is described as passing through two main exchanges, equipped with group selectors, and two " satellites " or district offices, at which only linefinders and line-selectors are provided. The claims in the present Specification relate to features of the metering arrangements. The operation of the calling subscriber's meter takes place during the release of the connexion and is dependent on the previous energization of a relay at the first selector, the circuit of this relay being completed over the called subscriber's line when the called subscriber lifts down his receiver. Other features of the system are claimed in the divided Specifications 12,423/13, 12,424/13, 12,425/13, and 12,426/13. Construction of selectors, line-finders, sequence switches, &c. The selectors and line-finders employed are power-driven switches of the construction described in Specifications 16,867/11 and 16,151/12 respectively. The selectors are 200-point switches . having their terminals arranged in ten levels of twenty sets each, and are provided with tripping-spindles for tripping a selected set of brushes to determine in which level a connexion shall be made. They are provided with devices for. closing a control circuit intermittently as they perform their selective movements, the selective system employed being of the type in which " reverting " impulses are sent back from the selectors to the operator's controlling - equipment. The line - finders are single-coordinate switches which have no normal position but remain on the terminals through which they extended a connexion in their previous service. The sequence switches employed to control the succession of operations in the different trunk circuits are power-driven switches having a number of cams controlling spring contacts, as described in Specification 20,840/09. Each sequence switch is represented by its power magnet 100, Fig. 1, and contacts 101, 102, 103, &c. Every time it is taken into use, it passes through a cycle of positions and eventually returns to its normal or first position. The power magnet 100 is controlled by a contact 101, which is closed except in the position indicated by the adjacent numerals. These numerals indicate therefore the positions in which the sequence switch is capable of coming to rest (in this instance the first, third, seventh, and eighth). In the case of the remaining contacts 102, 103, &c., the adjacent numerals indicate the positions in which the respective contacts are closed. A plus sign indicates that a contact is closed continuously between two positions, for instance, the contact 113 top is closed only in the first position, while the contact 113 bottom is closed continously between the second and seventh positions. The distributing-switch 600, Fig. 6, and the operators' registers 901, 902, &c., Fig. 9, are constructionally similar to sequence switches and are similarly represented. General operation of the system. Figs. 1, 2, 3, 4, and 5 should be assembled side by side, Fig. 6 below Fig. 2, Fig. 7 below Fig. 6, Fig. 8 to the right of Figs. 6 and 7, and Fig. 9 to the right of Fig. 8. Figs. 1, 2, 3, 4, and 5 represent a completed connexion between two subscribers, this connexion including a line-finder, Fig. 1, at the " satellite " or district office to which the calling subscriber belongs; a second line-finder, Fig. 2, at a main or controlling exchange; first and second group selectors, Figs. 2 and 3, at the same exchange; a third selector, Fig. 4, at a second main exchange; and a final selector, Fig. 5, at the satellite or district office to which the called subscriber belongs. The connexion includes repeating-coils at the first and third selectors, that is, at the two main exchanges. The inter-office connexions consist in everv case of two - conductor trunks. A calling subscriber is connected by the first and second line-finders to an idle first-selector, and then by a distributing-switch 600, Fig. 6, individual to the first selector, he is further connected to a disengaged controlling-equipment of an idle operator. The operator enquires the wanted number and writes it down on her keyboard, represented at the right of Fig. 9, and the extension of the connexion through the various selectors then proceeds automatically under control of her equipment, Figs. 7, 8, 9, which is released for further service as soon as the connexion is completed. Each first-selector trunk is equipped with supervisory signals and the release of the connexion remains under the control of the operator, at whose position the supervisory signals are situated. In reading the following detailed description of the operations it should he noted that, with a few exceptions, the first digit of the reference numeral indicates the Figure to which it belongs. First line-finder, Fig. 1, and second linefinder, Fig. 2. When the subscriber lifts down his receiver, his line relay 116 energizes a pilot relay 117, which energizes the power magnets 150 of all the disengaged line-finders serving the group of lines to which he belongs. As soon as the brushes of one of these switches arrive on the terminals of the calling subscriber, its testrelay 126 is energized and closes a low-resistance circuit through a second winding, so as to make it impossible for the test-relay of another linefinder to become energized over a multiple of the terminal 121. When the brushes 122 &c. are centrally alined with the terminals 118 &c. the ground connexion at the interrupter 128 is removed and the relay 127, becoming energized in series with the relay 126, cuts out the power magnet 150, energizes the holding-magnet 151, and drives the sequence switch 100 into its third position. The cut-off relay 129, energized over the terminal 120 and contact 110, reenergizes the relays 116, 117. The relay 127 is now kept energized by a circuit over the calling subscriber's line, so that, if he should hang up his receiver before the connexion is extended through the second line-finder, the relay is deenergized and drives the switch 100 forward to its normal position. In the third position of the switch 100, the contact 107 bridges the outgoing line to the central station, where a group of second line-finders, Fig. 2, are thereby set in action, one of which fixes itself on the terminals 233 &c. in exactly the same manner that has been described for the first line-finder. As the switch 200 passes from its first to its fifth position, the contacts 224 top, 225 top connect alternating current (represented by a circle enclosing plus and minus signs) to the incoming line, energizing the relay 132, Fig. 1, which drives the switch 100 into its seventh position, in which the subscriber's line is connected through to the central station, the relay 127 being kept energized over the contacts 114 bottom, 106, 104 bottom. Connexion to a disengaged operator's equipment by the distributing-switch 600, Fig. 6. Each first-selector trunk, such as that shown in Fig. 2, can be connected to either of two operators for controlling the numerical selection. Preference is however given to the " home " operator, before whom the supervisory signals individual to the trunk circuit are situated, and connexion is only made to the " alternate " operator if the ' home ' operator is busy. Each operator has a keyboard and two registering and sending equipments. If the ' home ' operator is idle, that is to say if her sequence switch 700 is in its normal position, the switch 600, which is individual to the selector trunk shown in Fig. 2, moves into its eleventh position, connecting the selector trunk to her A-equipment; or, if the sequence switch 800 of the A-equipment has not yet returned to its normal position, the switch 600 moves only to the ninth position, connecting to the B-equipment. If the home operator is busy, and if the alternate operator is idle and has depressed her helping- out key 771, then the switch 600 moves only to its seventh or fourth position, connecting to the A or B equipment of the alternate operator. It will be assumed' that the home operator is idle and her A-equipment disengaged. The contact 207, in the fifth position of the switch 200, lights the call-lamp 245 at the home operator's desk and drives the switch 600 to its second position. The home operator's sequence switch 700 being in its normal position, a circuit is closed for the relay 636, which closes a circuit through a second winding of its own and through relays 638, 639, and 716, the last of which drives the switch 700 to its second position. (If the alternate operator is idle and her helping-out key 771 depressed, the relay 637 is similarly energized and causes her sequence switch 750 to be driven to its second position, but the switch 750 in this case merely rotates until it returns to normal.) If several selector trunks should be trying simultaneously to connect themselves to the home operator, their respective relays 636 will at first be all energized, but when the relay 716 becomes energized, opening the circuits of the left-hand windings of the relays 636, the right - hand windings, which are not so highly wound, will not receive enough current through the resistance 739 to energize more than one of them, and the armatures will drop back until only one of the relays 636 is left in circuit. In the second position of the switch 700, the resistance 739 being now short-circuited by the contact 705 bottom, th