Patent GB-130329-A (GB)
Title: Telephone Exchange System.
IPC: H04Q3/42
Filed: 1919-07-22
Abstract: 130,329. Western Electric Co., (Assignees of Lundell, A. E., and Stearn, F. A.). July 22. 1918, [Convention date]. Semi-automatic exchange systems.-In a system in which an exchange operator controls numerical selectors to build up the wanted connexion, a cord-circuit, when taken into use, is automatically connected to an idle sending-equipment by means of a link circuit, terminating at one end in a plurality of cord-finding switches, serving different groups of the operator's cordcircuits, and at the other end in a hunting switch which gives access to a series of sending-equipments common to all the operators. Each operator has a single keyboard and several (say three) link circuits, which are taken into use in rotation. If either of the switches of a link circuit fails to perform its part, the link-circuit is released and the next one brought into action. As soon as the cord-circuit has been connected to a sending-equipment, a relay is energized to associate the linkcircuit with the operator's keyboard. The keyboard is released as soon as it has recorded the wanted subscriber's exchange and number on registers in the sending-equipment, and the sending-equipment and link circuit are released as soon as the wanted connexion has been established under control of the registers. Other features of the system described are claimed in the divided Specifications 143,551 and 143,908. General arrangement. Figs. 1 to 16, when assembled as shown in Fig. 17, form a single circuit diagram. A call from a subscriber 1, Fig. 1, is answered at an operator's manual board, and the exchange and number of the wanted subscriber are written down by the operator on her kevboard. If conversation is desired with subscriber 201, Fig. 4, at an automatic exchange, tha connexion is made by first and second selectors, Figs. 1 and 2, which select a line to the wanted ex- .change, and by an incoming group selector, Fig. 3, and final selector, Fig. 4, at this exchange. On the other hand, if a subscriber 250, Fig. 5, at a manual exchange is wanted, a line to this exchange is selected by the first selector. Fig. 1, (or it might have been by a second selector), and the number of the wanted line is illuminated on a numerical indicator, Figs. 6 and 7, to enable an operator to complete the connexion. Both of these operations will be described hereafter. When a cord-circuit, Fig. 1, is taken into use, an idle link-circuit, Figs. 8 and 9, pre-selected by an allotting-switch 400, Fig. 8, connects itself (1) by one of a pair of finding-switches A, B, Fig. 8, to the cord-circuit, (2) by a hunting-switch, shown at the right of Fig. 9, to an idle sending-equipment. Figs. 12 to 16, and (3) by a relay 937, Fig. 9 to the operator's keyboard. Figs. 10 and 11. Construction of switches. The selectors, Figs. 1, 2, 3, 4, are power-driven switches of the type described in Specification 24928/13, with 500 sets of terminals arranged in a single vertical series. The terminals are divided into five groups of 100. corresponding to five sets of brushes, anv set of which can be tripped to engage with the terminal bank. The 100 sets of terminals served by each set of brushes are divided into 10 groups of 10. or in some cases into 4 groups of 25. The shaft which carries the five sets of brushes is moved up in three successive stages; the first movement brings one of the sets of brushes into tripping- position; the second movement (a tripping-magnet being now energized) trips the selected brushes and carries them to one of the groups of terminals to which they have access; the third movement positions the selected brushes on a particular set of terminals (or on the first idle set) of the selected group. As the shaft moves up, a commutator sends back reverting impulses to control the movement. The sender-selector shown at the right of Fig. 9 is of similar construction, with the simplifications that arise from its being a mere hunting-switch, with a single set of brushes. The sequence switches 10, 100, 150, &c. are of the type described in Specification 1154/14, and the allotting-switch 400, cord-finders 425, 450, and class-register 800 are of the same construction. The switch 300 differs in being ratchet-driven. The sequence switch contacts shown in each figure are controlled by the switch shown in that figure or (in Fig. 8) by the switch shown in the same part of the figure marked off by a broken line. The positions in which each contact is closed are shown by the adjacent numerals. Allotting switch, 400, Fig. 8, for pre-selecting. an idle link circuit. One of these switches is associated with the group of link circuits belonging to each operator. The operator may have three link circuits, connected to positions 1, 2, and 4 of switch 400, the spare position 3 being connected direct to earth so as to be automatically passed over. In the present case the switch 400 is supposed to be in position 4, connecting the circuits 403, 406 from the operator's cords to the link circuit shown in Figs. 8 and 9; from this position it will be moved on, to find another idle link circuit, as soon as the circuit 417 is closed by the sequence switch 900 in its 9th position, i.e. when the brush-selecting operation of the first selector, Fig. 1, has been completed. If all the link circuits are busy, the switch 400 stops in position 5, from which it is moved forward as soon as the circuit 418 is closed by the return of any linkcircuit sequence switch 900 to its normal 1st position. Operation of the link circuit, Figs. 8 and 9, to connect the cord circuit, Fig. 1, to an idle sending-equipment, Figs. 12, 13, 14, 15 and 16, and to associate the sending-equipment with the operator's keyboard, Figs 10 and 11. The relay 7, energized when the operator plugs into the calling line 1, closes a circuit 12, 27, 13, 14 for a relay 11, which energizes a relay 15, which closes a circuit 16, 17, 18 for moving the sequence switch 10 to its 2nd position. In this position the relay 14 becomes energized in series with the relay 11, (being no longer short-circuited through the contact 12) and connects the operator's telephone to the calling line. The operator is supposed to have charge of 24 cord-circuits, 12 of which are accessible to the link circuit through a cord-finder A, Fig. 8, and the other'12 through a cord-fiiider B, connected in parallel with A.. The cord circuit shown in Fig. 1 belongs to the group served by the cord-finder A, which (as well as its twin cordfinder B) is in its normal 17th position, and the A cord-finder magnet 425 is now energized by a circuit 426, 901 (Fig. 9), 902, 451, 402, 403, 16, 17, 18, and moves the cord-finder to its 18th position, where it closes a circuit 906 to energize the relay 903, Fig. 9. The relay 903 closes a circuit 908, 907 to move the sequence switch 900 to its 3rd position, in which a circuit is closed for the selector lifting magnet 914. As long as the testbrush 912 passes over the grounded multiples of busy senders the relay 903 is kept energized by a circuit 909, 910, 911, and while the brushes are passing from one set of terminals to the next, the relav 903 is kept energized by a commutator circuit 904, 917, 918, 919. 915, 908, but as soon as the brushes a.re centred on the terminals of an idle sender the relay 903 de-energizes, open-circuiting' the lifting-magnet 914 and closing a circuit 921, 920 to drive the switch 900 to its 5th position. in its 3rd position the switch 900 also closed a circuit 923,.934 to drive the cord-finder A out of its 18th position, and the cord-finder moves forward to find the cord-circuit, shown in Fig. 1, at the same time that the sender-selector is hunting for an idle sender. In the present case the cord-circuit shown in Fig. 1 is supposed to be connected to the 5th position of the finder 425, and when the finder reaches the position 4¥ a relay 924, Fig. 9, is energized over a circuit 928, A21, 430, 24, 23, 406, 405, 927, 926, 925; the relay 924 open-circuits the switch 425 so that it stops in its 5th position, and energizes the relay 930, which drives the switch 900 to its 7th position. In the 6th position of the switch 900 the contact 931 closes a circuit for relays 937 and 602 (Fig. 11) ; the relay 937 locks this circuit so as to be independent of the relay 924 and completes the connexions between the link circuit and the operator's keyboard, Figs. 10 and 11. Operations when a link circuit fails to function successfully. If the sender selector, Fig. 9, fails to find an idle sender, the commutator brush 919 comes to rest on the overflow contact 976, closing a shunt round the relay 924, so that. this relay is prevented from energizing when the switch 425 reaches its 5th position. The switch 425 in this case goes on to its 16th position, in which the contact 427 closes a circuit 978 to drive the switch 900 from its 5th to its 7th position, in which a circuit is closed through the back contact of relay 924 and contact 923 to drive the switch 900 to its 15th position. The contact 923 now closes a circuit 431 which drives the switch 425 to its normal 17th position, where it closes a circuit 972 to drive the switch 900 to its 16th position, energizing the down-drive magnet 979. When the brush 919 reaches the normal segment 975 a circuit is closed to move the switch 900 to its normal 1st position. In the 13th position of the switch 900 the allotter 400 was moved out of its 4th position to find the next idle link circuit, which is then operated to establish the desired connexion. The same sequence of events occurs if the cord-finder A fails to operate properly, i.e. if the relay 924 fails to become energized when the finder reaches the position to which the cord-circuit, Fig. 1, is connected. Setting of the sending registers, Figs. 14, 15, and 16, by the operator's keyboard, Figs. 10 and 11 : system of translation. The operator's keyboard comprises hundreds, tens, a