Patent GB-208194-A (GB)
Abstract: 208,194. Siemens Bros. & Co., Ltd., and Grinsted, W. H. Aug. 12, 1922. Automatic exchange systems. - A subscriber operates a set of temporarily-used Strowger-type switches to mark a desired group of inter-exchange or other junctions and is then connected over two or more non-numerical switches to an idle trunk in the marked group. In the system partly shown in Fig. 5, each group is associated with a marking relay S<a>, S<b>. The connection is completed over three ten-point switches such as 3, 14, 12. Each marking relay S is adapted to short-circuit a normally energized relay GP3 associated with it. Each relay GP3 when shortcircuited marks all switches 12 capable of making a connection to the group .associated with it over their starting relays to make them selectable by switches 14 and also short-circuiting a relay GP2. Each relay GP2 exercises a similar function in regard to switches 14 and a relay GP1. The relay GP1 controls the starting of all switches 3. As each trunk is taken into use a bridge ja<1> is removed so that if all trunks in a wanted group are in use the marking relay S cannot short-circuit its GP relay. As each switch is ,seized the shortcircuit made by its GP relay across the GP relay of the preceding switch is broken to prevent interference with subsequent calls. Only one call can be completed at one time, later calls being stored and completed in succession. The system is described in detail with reference to Figs. 1 - - 4. Selection of marking relay. A subscriber on removing his handset is connected to an idle repeater I, Fig. 1. Relay A energizes over its winding 1 and energizes slow-release relay V which connects relay E to the incoming o-wire. Relay E breaks the initial circuit of relay A which however is held over its windings 2, 3 by the subscriber's loop. Relay V also energizes the driving magnet D<2> of a preliminary selector 2 which hunts for an idle numerical selector 4 under control of the test relay T<2>. When this is found, relay AA, Fig. 2, energizes the slow-release relay D which sends back dialling tone into the awire. The subscriber then dials the first exchange digit and relay A, Fig. 1, repeats the impulses to relay AA which operates the vertical magnet HM. The change-over of vertical off-normal contacts K<2>, K<3> causes relay D to release at the end of the digit, completing a circuit through an interrupter for the rotary magnet DM until, on the finding of an idle final selector, relay TA operates. Relay TA locks up over its second winding, grounds the c-wiper, releases relay AA and connects up the a and b wipers. At the final selector 5, Fig. 3, relays AB, N pull up and energize a slow-release relay DA which prepares the vertical circuit. Magnet HM<1> is thus operated in accordance with the next digit whereupon relay DA falls back and energizes relay G, which switches in the rotary magnet DM<1> and re-energizes relay DA to complete a holding circuit for relay G. The single wiper A<1>, which co-operates with terminals connected to group-marking relays, is then stepped to the desired contact and relay DA falls back releasing relay G which connects the wiper A<1> to the lefthand end of relay L. Establishment of talking connection. If now the equipment is not in use in extending another call, the selected relay S energizes in series with relay L in a manner to be described later. Relay S grounds the wire 21 and connects battery over relay GA to a point 20 connected to' a number of relays U, one for each trunk on the selected group. Relay GP3, Fig. 2, is short-circuited and falls back short-circuiting relay GP2 and applying battery to the starting relays RD of all switches 7 capable of extending the call. Relay GP2 falls back, short-circuits relay GP1, Fig. 1, and marks all switches 6 capable of extending the call by connecting battery to their starting relays RC. Relay GP1 falls back and connects battery to the starting relays R of all switches 3. When the equipment becomes available for extending the call, the d-wire connected to the preliminary selector 2 is grounded. The starting relay R of the switch 3 associated with the repeater set 1 is thus energized and completes a circuit for the driving magnet D<1> which moves the wipers A<1>, B<1>, C<1> until the c-wiper encounters a marked terminal whereupon relay T<1> stops the driving magnet and extends the a and b wires to the switch 6. Relay RC at switch 6 energizes, completes a circuit for driving magnet D<6> and opens at rc<3> the short-circuit across relav GP1. When the wipers find a marked switch 7, relay TC operates, stops the driving magnet, removes a short-circuit from the high-resistance opposition winding of relay RC and extends the a and b wires. Relay RC releases, breaking the circuit of winding 1 of relay TC which is held however over its winding 2. The switch 7 is controlled similarly to the switch 6, and when an idle trunk is found relay TD energizes in series with the relay J of the selected trunk and relay GA. Relay J energizes and locks up in a circuit independent of relay JA, and energizes relay JA. Relay JA locks up in a circuit independent of relay J and opens one of the bridges between conductors 21, 22 previously referred to. Arrangement for dealing with calls in succession. When relay AB, Fig. 3, first released in response to impulses of the last digit, relay RB energized, locked up over its second winding and completed a circuit through an interrupter for the driving magnet D<3> of a switch 8. The a and b terminals of switch 8 are connected to corresponding a and b terminals of a " controller " 9, Fig. 4, and the c-terminals to a-terminals of a controller sequence switch 10 the b-terminals of which are connected to the c-terminals of the switch 9. The wipers of switch 8 are driven until they are on the terminals (say the 5th) corresponding to those on which the wipers of the switch 10 are resting, whereupon relay TB energizes in series with relay RA of the switch 10, locks up over its second winding, cuts the driving circuit of magnet D<3> and connects relay L and the selected relay S in series to the b-wiper. Relay RA operates the driving magnet D<5> to move the switch 10 into its next 6th position. If now there are no waiting calls, the switch 9 will also be in its 5th position and relays S, L, C' energize in series. Relay S controls the completion of the call as described above. Relay L releases relay RB. Relay C<1> disconnects its driving magnet D<4>, earths the c-wiper to energize starting relay R at the first selector, and energizes relay B<1> which locks up independently of relay C' and prepares a circuit so that when, on the completion of the connection relay C' falls back, as described later, the driving magnet D<4> is operated and the wipers of switch 9 are moved to their 6th position, short-circuiting relay B<1> again. If another call comes before the former is completed, the switch 8 of the final selector used will be stopped in the 6th position and the switch 10 will be moved to its 7th position. The selected marking relay, however, will not be energized until on the completion of the earlier call the wipers of switch 9 also move to their 6th position. A third call coming in before the completion of the first would cause a switch 8 to stop in its 7th position, the circuits of the selected relay S remaining uncompleted until earlier calls have all been put through. Release of setting-path. The energization of relay GA, Fig. 3, on the finding of an idle trunk cuts in the high-resistance winding of relay S and relay C, Fig. 4, falls back and releases relay R at the preliminary selector, Fig. 1 . Relay T<2> falls back, disconnects the repeater from the numerical switches, and releases relays TA, N which operate the release magnets of the respective selectors. Relay N releases relay TB and the numerical switches can again be used for further calls. Release of talking-path. When the calling subscriber hangs up relay A falls back and releases relay V, which releases relays T<1>, TC, TB, JA. The switches remain in the position in which they were last used. Specification 7531/13 is referred to in the Provisional Specification.