Patent GB-320923-A (GB)
Title: A switch arrangement for line intercommunication switches with multiple lines
IPC: H04Q3/00
Filed: 1928-07-23
Abstract: 320,923. Merk, F. July 23, 1928. Automatic exchange systems.-Connectors, the currents of which are not themselves modified, are enabled to select an idle line from a multiline group, by providing each such group with auxiliary apparatus which connects itself to a connector calling the group and either delivers impulses continuously to the connector stepping magnet, the impulsing circuit being broken by the ordinary test relay when the connector reaches an idle line, or hunts for an idle line, releases the connector and then sends it two trains of impulses to set it to that line. In the latter system the lines of a group can appear anywhere in the connector bank. The invention is described with reference to a system using the switches described in Specification 275,255 having a single stepping magnet H<1> for the wiper choosing and line selecting movements and a magnet S for tripping the selected wipers. Call finder. Line relay T starts an idle call finder over circuits, not shown. During the stepping movement, a sluggish relay CI connects up the test relay VI. When the line is found, VI pulls up, locks over a low resistance winding, and energizes R. Operation of connector for calls to ordinary and night service lines. The first digit is repeated at a<3> to H'. At the first step an off-normal contact brings into circuit a relay VII of a type which is slow to energize though quick to fall back, and at the end of the digit this relay pulls up and energizes magnet S, to trip the selected wiper set in series with relay VIII. The latter cuts in its high resistance winding to release the trip magnet. At the first impulse of the second digit, VII falls back and unlocks R, VIII remaining locked over a back contact of VII. The stepping magnet responds to the second digit, at the end of which VII pulls up again and releases VIII. In the interval before VIII falls, a test circuit is completed through P. If the line is idle, P pulls up, locks to the test wire over its low resistance winding and sends out ringing current over Q. When the called subscriber replies, Q switches through and shunts out P but remains locked to the test wire over a. low resistance winding, a short-circuit on which is removed by the back bridge relay Y. Release. This is under the control of the called party. The relapse of Y shunts out Q and a stepping circuit is made for H<1> which drives the selector to its releasing position. Operation as rotary connector, 1st arrangement. When a multiline group is called, the connector is set to a position from which there is no outgoing line, the b and c terminals being connected to the auxiliary apparatus, Fig. 2, of the group in question. Relay CII energized in the test circuit energizes a relay U which interacts with the driving magnet DI of a hunting switch I for associating the auxiliary apparatus with the connector, and makes an alternating current test circuit in which, when the connector is found, W pulls up over circuit 1, energizes VII in the connector over circuit 2, and magnet DII of an impulse sending switch II in the auxiliary apparatus. DII releases U and drives the switch II one step, whereupon CII, P, W fall back, and a new circuit is made for U which now interacts with DII to drive the sending switch on to normal. Each energization of U now sends an impulse to H<1> over circuit 3 until an idle line is encountered when the impulse circuit is opened by P which rings the line as described above. Operation as rotary connector, 2nd system. The b and c terminals of the position designating a group are connected to the apparatus shown in Fig. 3, and the test wires of the group are connected to the bank CO of a hunting switch II in the auxiliary apparatus. When the group is called, CIII makes a driving circuit and an alternating current test circuit for switch I which hunts for the calling connector. When the latter is found, WIII locks itself temporarily and energizes K over circuit 2 in series with VII which cannot pull up in this circuit, and the c circuit is opened at k<5> so that CIII, P, WIII fall back. On the relapse of P, VII being energized, the restoring circuit for the connector is completed. K completes driving and test circuits for the switch II which is stopped by PIII on the 1st idle line. When the connector reaches normal, K falls, and assuming PIII has pulled up, AIII pulls up over circuit 1 in series with S which remains unoperated, energizes VII over circuit 2, and makes a driving circuit for the sending switch III which at each step sends an impulse to H<1>. When III reaches the position corresponding tc the tens digit of the idle line, a circuit is made over IIt, IIIt and circuit 1 for the tripping magnet S, and when it reaches the position corresponding to the units digit, WIII pulls up over IIIu, IIu in series with AIII connecting up P over circuit 4 to stop the connector and ring the line and cutting off PIII.