Patent GB-181120-A (GB)
Abstract: 181,120. Relay Automatic Telephone Co., Ltd., and Johnson, B. B. March 7, 1921. Automatic and semi-automatic exchange systems.-In systems of the type in which a selective connection is temporarily set up over one path and is released when a permanent talking connection is set up over another path, a smaller number of dialling digits is required, and less switching apparatus is used, to extend connection to a trunk leading tn a distant exchange, than to extend connection to a local subscriber. The invention is described as applied to a system using relays throughout, in which an impulse responding device, as described in Specification 181,119, is temporarily associated with a calling line to establish a marking circuit particular to an individual local line or to a group of exchange trunks. connection to which, or one of which, is then extended by a non- numerical relay connecting organization comprising three sets of intermediate lines. Fig. 1 shows the arrangement of trunks for extending connection to groups of trunks E<2>, F<2> outgoing to distant exchanges, or to incoming trunks IT<1> and links L<1> leading to local subscribers. An X at the intersection of two lines marks the possibility of a connection. Each group of incoming lines A, B, &c. has access to a corresponding group A<1>, B<1>, &c. of first intermediate lines, any line in group A being connectible to any line in group A<1>, &c. Each first intermediate line has access to one line in each group of trunks E<2>, F<2> and to one line in each of the groups of second intermediate lines A<2>, B<2>, &c. Each group of second intermediate lines A<2>, B<2>, &c. has access to a corresponding group of third intermediate lines A<3>, B<3>, &c. It will be seen that there are a number of alternative routes from a given incoming line to a local subscriber or to a distant exchange, and of these a route must be pre-selected of which no segment is engaged. If more than one group of outgoing trunks (which may have the same or different numerical designations) are allocated to the same distant exchange, the groups are tested simultaneously, and if no idle line exists in any groups no test is made within the groups, but a metering-device is operated to record the number of times no trunk was available. If, however, any groups contain idle lines, a group is first found in which an idle line or lines exist, and a test is made for an idle line in this group. The circuits referred to in this abridgment by numbers of 50 and over are also to be found in the drawings accompanying Specifications 181,116 and 181,117, the figures of which, together with those of the present Specification (in which only the test circuits are shown) should be arranged as indicated in Fig. 7. Connection with a local subscriber S<2> assuming the route Aa, A<1>a, A<2>a, A<3>b, IT<1>, L<1>, Fig. 1, is taken. The calling subscriber is connected to the outgoing trunk Aa as described in Specification 181,116, and the numerical impulses are received by a relay selector (as described in Specification 181 119) and operate a marking wire relay set. The outgoing trunk marking relay OTM<1>, Fig. 2, is thereby energized in a circuit 1, and a making circuit 50 is completed for the line relay LE<2>, Fig. 1, Specification 181,116, of the called subscriber S<2>, and a relay D, Fig. 4, Specification 181,116. The relay OTM<1> completes test circuits 6, 7, 8 for the first intermediate lines A<1>, the marking relays OLM of which energize and prepare circuits 9 to 20 for the marking relays ILM, Fig. 3, of the second intermediate lines A<2>, and also prepares circuits 3, 4, 5, for the connecting relays OLC, LCC, ILC of the first, second and third intermediate lines A<1>, A<2>, A<3> respectively. If a first intermediate line A<1> is busy, its busy relay OLB is energized and breaks the test circuit for the corresponding marking relay OLM, whilst if second or third intermediate lines A<2> or A<3> are engaged the circuits of their marking relays ILM or ITM are broken at relays ILB or ITB respectively. Whilst these operations are taking place, relays D, Fig. 4, Specification 181,116, closes circuit 51 for the incoming trunk test relay ITT<1>, and assuming the incoming trunk IT<1> is capable of extending the call, a circuit 53 (a continuation of circuits 9, 13, 17) is completed, in which the incoming trunk marking relay ITM, the incoming trunk connecting relay ITC<1> and the link marking relay LM<1> are energized. The response of the relay LM<1> in circuit 53 completes the already prepared circuit 52 for the connecting relay LC<2> which connects the subscriber S<2> to the link L<1>, which in turn is extended to the incoming trunk IT<1> by the connecting relay ITC<1>. The relay ITM, Fig. 3 of the present Specification, prepares the circuits 3, 4, 5, and energizes the relay SS, which disconnects the circuits 9, 13, 17 from the circuit 53 and connects them over the contact 9a. The relay ILM<1> now energizes cut-out relays ILM<2>, ILM<3> 'and completes the circuit 3, in which the connecting relays OLC<1>, LCC<1>, ILC<2> respond and extend the calling line over the intermediate lines A1<a>, A2<a> and A3<b>. A holding circuit 54, 55 is also completed in which relays OLB<1>, ILB<1>, ITB<2> energize to mark the intermediate lines busy, relay LB<1>, Fig. 3, Specification 181,116, energizes to mark the link L<1> busy, and the cut-off relay CO<2>. Fig. 1, Specification 181,116, operates. Relay CO<2> energizes a relay F<2> which opens circuit 50, de-energizing the line relay LE<2> and the relay D. whereby the circuit 53 is opened and the link marking relay LM<1> released. The cutoff relay CO<2> also disconnects the line relay LE<2> from the called line, so that this relav does not operate when the called subscriber replies. Ring- ing takes places on the energization of the relay ITB<2>, as described in Specification 181,117. Connection to a trunk in a group E<2>, F<2>, or G<2>, Fig. 5, when all of these groups lead to the same exchange. Assuming a calling party is connected to the outgoing trunk B<a>, Fig. 2, and that the impulse-responder having been set to the first digit has brought about the energization of a relay JME, Fig. 5, in a circuit 23, relay OTM<4> energizes, completing circuits through the marking relays OLM<4>, OLM<5>, OLM<6>, and preparing circuits 25, 26, 27 through the connecting relays OLC<4>, OLC<5>, OLC<6>. The relays OLM<4>, OLM<5>, OLM<6> prepare circuits 28, 29, 30 which unite at the contacts of the relay SSE with a circuit continuing through relay GSE to battery at a contact of relay JME. A simultaneous test of the other groups is also made over similar circuits 34, 35 through the group relays GSF, GSG, but if an idle line exists in the group E<2>, the response of relay GSE disconnects the relays GSF, GSG of higher groups. Relay GSE also locks up and energizes the relay SSE which breaks the circuits 28, 29, 30 at its left-hand contacts and completes them over its right-hand contact, thereby energizing the marking relays OJM associated with idle trunks. The response of the lowest relay OJM' cuts out all those above it and completes the prepared circuit 25 for the connecting relays OLC<4>, OJC<1>, which connect the outgoing trunk B<a> to the exchange trunk E<2>a over the first intermediate line B<1>a, and lock up in series with the busy relays OJB<1>, OLB<4> over a holding circuit 33. If all the trunks in the group E<2> are engaged, relay GSE will not energize since the circuits 28, 29, 30 are broken by the relays OJB, but a circuit 34 is completed for the group relay GSF of the trunking group F<2>, which is tested in the same manner as the group E<2>. Similarly, if all the trunks in the second group are busy, a third group may be tested by the relay GSG. The groups E<2>, F<2>, &c. although leading to the same exchange may be allotted different numbers with a view to subsequent re-allotment to different destinations by disconnecting the conductors GS<1>, GS<2>, GS<3>. When connected as shown, however, although a relay JME, JMF or JMG appropriate to the number dialled will be energized, the three groups will be tested simultaneously as previously described, but the group appropriate to the number dialled will have precedence. If no trunk is available in any group a circuit is completed for a metering device 36. Connection to a trunk in group E<2>, F<2> or G<2> when these groups lead to different exchanges. In this case the conductors GS<1>, GS<2>, GS<3> are disconnected. A call to the group E<2>, say, will proceed as described in the previous paragraph. No group test, however, is made since if no line is idle a circuit cannot be completed for the group relays GSF or GSG. The response of relay JME and the failure of relay GSE to energize may be used to operate a recording device. Specifica tion 142,265 also is referred to.