Patent GB-190720-A (GB)
Title: Improvements in automatic or semi-automatic telephone exchanges
IPC: H04M3/523
Filed: 1922-12-19
Abstract: 190,720. Janson, G. H. Dec. 20, 1921, [Convention date]. Automatic and semi-automatic exchange systems.-A call distributor common to a plurality of groups of calling lines comprises a number of primary relays PR, Fig. 1, one allotted to each group of calling lines, and a number of secondary relays SR equal in number to the calling lines in each group and connected in multiple to contacts of the primary relays PR, the relays PR, SR controlling the calling line marking circuits, and being so arranged that only one relay of each series can be maintained operated at the same time, thus preventing simultaneous calls in the same or different calling-line groups. In the arrangement shown in Fig. 1, the marking wires MS<1>, MS<2> control the circuits of the vertical and horizontal magnets MR<1>, AR<1>, of cross-bar callfinder switches KV of known type associated with outgoing trunks FL<1>, each of which is connected in parallel to all the contact sets KG<11> of a separate switch KV, the calling lines AL<1> being multipled in all the switches KV. Assuming a line AL<1> in the group G<1> is calling, the response of line relav LR<1>, completes a circuit 2 for the primary relay PR<1>, which locks up in series with a relay BR and energizes the secondary SR' in a circuit 4. Relay BR opens the initial energizing circuit of all the relays PR<1>, PR<3>, &c. to prevent the energization of another of these relays until the call in question has been dealt with, whilst relay PR<1> at contact K<2> opens the holding circuit of subsequent relays PR<2>, PR<3>, &c. to prevent simultaneous calls in different groups. The secondary relay SR' locks up in series with a relay CR, which prevents the energization of another relay SR. The relay SR' opens at contact R<4> the holding circuit of the succeeding relays SR<2>, SR<3>, &c. thereby preventing simultaneous calls in the same group G<1>. Relay CR energizes a slow-acting relay DR and closes a circuit 5 for the group relay GR<1> of a switch KV<1> associated with an idle outgoing trunk FL<1>. The vertical and horizontal magnets MR<1>, AR<1> are thereby energized in circuits 6, 7, ,and the calling line is connected to the outgoing trunk FL<1> over the contacts KG<11>, microphone current being supplied over the relays RR<1>, RR<2>, the latter energizing a relay TR which closes a holding circuit 8 over the cut-off relay UR. Relays LR<1>, SR<1>, CR are then de-energized, and a momentary circuit 9 is closed through relay BR, the relay PR<1> being short-circuited at the same time. De-energization of the relay CR is followed by the relapse of relays GR , DR, BR, and the call-distributor is restored to normal. In the modification shown in Fig. 2, auxiliary relays HR<1>, HR<2>, &c., energized by the prinary relays PR<1>, PR<2>, &c., control the marking circuits, whilst a chain of relays OR<1>, OR<2>, &c. operate as a trunk searcher. Each calling line is connected in parallel to all the contact sets of a vertical row of a switch KV<1>, and each outgoing trunk FL<1> is connected in parallel and in multiple to a horizontal row in each switch KV<1>. A call proceeds as in the first arrangement, a primary relay PR<1> energizing its auxiliary relay HR<1>, which closes a circuit 10 for a group relay GR<1> and energizes a secondary relay SR<1>, thereby causing the response of the vertical relay MR<1> controlling the calling line contacts in the switch KV<1>, over a circuit 11. A circuit 12 is also closed for a relay OR<1>, OR<2>, &c. corresponding to an idle trunk FL<1>, and a horizontal relay AR<1> responds in a circuit 13, thus extending the calling line to an idle outgoing trunk FL'. The closure of a holding circuit 14 restores the apparatus as in the first arrangement. The invention is also stated to be applicable to relay and mechanical call finders. Specification 13524/14 is referred to.