Patent GB-190927458-A (GB)
Title: Improvements in Automatic Telephone Exchanges.
Filed: 1909-11-25
Granted: 1910-08-04
Abstract: 27,458. Siemens Bros. & Co., [Siemens & Halske Akt.-Ges.]. Nov. 25. Automatic -exchange systems.- In systems of the type in which a calling subscriber is connected automatically with an idle first selector, a large number of first selectors is allotted to several groups of subscribers, and a calling line is connected to an idle selector through two intermediate switching- mechanisms. By this means, the total number of first selectors in an exchange is reduced, since the maximum percentage of simultaneous conversations is less in a large group of subscribers than in a small group. In the form of the invention shown in Fig. 1, each subscriber T<33> is provided at the exchange with a preliminary selector VW<33>, by means of which a disengaged second preliminary selector VW<1> is found, and this in turn selects an idle first selector GW in the usual manner. When the calling subscriber removes his receiver, his call relay R<33> is energized, and completes the circuit of the actuating- magnet D<33> through an interrupter U, whereby the wipers o<1>, o<2>, o<3> are stepped around until the wiper o' engages the terminal of an idle preliminary selector VW<1>, when the circuit of the test relay P<33> is completed from the battery G through a contact k<2> (closed when the switch VW<1> is in its normal position), relays R<1>, p<33>, resistance w<33>, and armature r<2> to earth. The relay P<33> locks-up over its armature p<4>, and disconnects the call relay and actuating-magnet, at the same time continuing the leads a<33>, b<33> to the wires a, b. The reduction in the potential of the lead c prevents any other first preliminary selector connecting itself to the switch VW<1>. The excitation of the relay R' completes the circuit of the actuating- magnet D'through the interrupter U, whereby the wipers o<4>, o<5>, o<6> are stepped around until the wiper o<6> engages the terminal of an idle first selector GW, when the test relay P<1> is energized and locks-up over its armature p<12>, at the same time disconnecting the magnet D' and continuing the leads a, b, c to the wires a, b<1>, c<1>. During the movement of the selector VW<1>, the test lead c is supplied with current over the contacts p<7>, r<5>, and relay R', and after the relay P<1> is energized over the contact p<9> and resistance w<3>. When the conversation is over, the relays P<1>, P<33> are deenergized and the magnets D', D<33> are again brought into action and return the switches to their normal position when the circuits of the magnets are opened at the contacts k<3>, k<1>. In the form of the invention shown in Fig. 2, the subscribers are arranged in groups of, say, one hundred, and to each group a number of call-finders is allotted, so that when a calling subscriber removes his receiver one of the call-finders rotates until it engages the terminals of the calling-line. The leads from the wipers of the call-finders of several groups of subscribers are themselves grouped, and terminate in the fixed contacts of a second series of callfinders, the wipers of which are respectively connected to first selectors of the Strowger type. The first set of call-finders are two-co-ordmate switches, having a hundred sets of contacts to which the subscribers' lines are multipled. The wipers of the various call-finders in one group normally rest opposite different horizontal rows of contacts, so that when a subscriber calls, the call-finder, bolonging to the row of contacts in which the subscriber is represented, is alone set in action, and reaches the calling-line with a maximum of ten steps, no vertical movement being necessary. As soon as any call-finder leaves its zero position, the call-finders serving the lower horizontal rows move up one step, and a call-finder from the reserve sets itself upon the lowest row. The second set of call-finders act in a similar way to connect up the operative first call-finder, and consequently the calling-subscriber, to an idle first selector. The subscribers T', T<14> are connected to different rows of the call-finders AS', AS' of the same group, the leads l<1>, l<2> and l<3>, l<4> of these callfinders being themselves connected to second callfinders AS<I>, AS" serving different groups of leads. When a calling subscriber T<2> removes his receiver, his call-relay AR' is energized and connects a resistance w<1> in parallel with one of the resistances w, thus increasing the current flowing through the winding r' of a relay B' sufficiently to energize this relay, which brings into circuit the rotary magnet D' of the call-finder AS' which is in position on the corresponding row. At the same time a locking-circuit is completed over the armature s', winding r', and a relay K<1> common to a group of subscribers. The magnet D' rotates the wipers u<4>, u<5>, u<6> along the contacts of its row until the wiper u<6> engages the contact of the calling-line, when a circuit is completed through the test-relay S' and one winding of the subscriber's cut-off relay TR<2>, which locks-up and cuts-off his call-relay AR<2>. The test-relay S' opens the locking-circuit of the relay B' and stops the rotation of the switch, and at the same time connects the leads a', b<2> to the wires l<1>, l<2> leading to the stationary contacts of a second call-finder AS'. The excitation of the relay B' not only brings into action the magnet D', but also connects a resistance w<5> in parallel with the high resistance w<4>, thus increasing the current through a winding r1<1> of a relay B' which causes the second call-finder to move round until its wipers rest upon the terminals of the leads l<1>, l'. The testrelay S<1> is then energized, disconnecting the relay B' and connecting the leads l<1>, l<2> to the leads l<5>, l<6> of a first selector. The de-energizing of the relay K<1>, which occurs when the relay S<1> is energized, completes a circuit through the relay A' of the call - finder AS' and a resistance w, whereupon the vertical magnet H' raises the switch AS' one step, so that its wipers are opposite the top row of contacts. The relay K<1> also closes the circuits of relays similar to A<2> in the other call-finders of the group, so that the wipers of each are raised to the next row. Further movement of the wipers is prevented by the arrangement that the relay A' of, say, the third call-finder is then connected in parallel with the winding r<1> of the relay B' of the second call-finder, and consequently the relay A' does not receive sufficient current to energize it. The circuit of the test-relay S<I> of the second call-finder includes a relay V<1> of the first call-finder, the relay V<1>controlling a release-relay O<1> which locks-up over its armature o<1>, and controls the release-magnets P<1>. In another form of the invention shown in Fig. 3, each of the first call-finders AS<1>, AS<2> is associated with a preliminary selector VW<I>, VW<II>, which selects an idle group selector. When a subscriber T<14> calls, the call-finder AS' connects itself to the calling-line as in Fig. 2, and the relay B<2> completes a circuit over the contacts r<5>, S<11>, S<10> for a relay B<II> of the preliminary selector VW<II>. The relay B<II> completes a holding-on circuit over the contact r<6>, and closes the circuit of the actuating- magnet D<II>, which rotates the selector until its wipers engage the contacts of an idle first selector, when the test-relay S<II> is energized and cuts-off the relay B<I>I. When the relay S<II> is de-energized at the end of a conversation, the actuating-magnet D<II> is again brought into circuit over contacts s<2>, i<3>, and returns the preliminary selector to its normal position, when the circuit of the release-magnet P' of the call-finder is completed.