Patent GB-154582-A (GB)
Abstract: 154,582. Betulander. G. A. Nov. 22, 1919, [Convention date]. Automatic and semi-automatic exchange systems and apparatus.-In call-distributing arrangements for automatic and semi-automatic telephone systems, the " marking-relays " allotted to each subscriber's line to mark it as calling are divided into a number of groups to each of which is allotted a group relay, which operates to control the circuits of the other groups of marking relays in such a way that when calls occur simultaneously in different groups only one marking relay can operate, or remain in its operated position. The invention is described, with reference to Fig. 2, as applied to the switching apparatus of the general kind described in Specification 141,657, in which 'a calling line L is extended to an idle trunk FL by the co-operation of horizontal and vertical members, controlling the switching contacts KG, these members being operated respectively by the connecting-relays AR, allotted to each junction line, and the marking-relays MR allotted to each subscriber's line. The marking- relays MR are divided into groups, one of which is shown, to each group being allotted a group relay GR. The operation of a marking-relay energizes the group relay of the group, which operates to open the circuit of all the other marking relays on the attraction of its armatures. Thus upon calls occurring simultaneously in two different groups only the line in the group located nearest the current source B is marked as calling. Assuming a call occurs on the line L3, the line relay LR3 completes a circuit 6 through the marking relay MR3 over the series contacts of all the group relays. Actuation of the relay MR3 closes a holding circuit 7 through the group relay GR3 which cuts out all the other marking relays and connects all the test wires of the junction lines to the corresponding test relays PR. The test relay PR2, nearest the battery B, connected to an idle trunk, for instance FL2, in energizing cuts out all the other test relays, and a circuit is completed through the operating winding AL of the relay AR2, which holds itself over the circuit 9 and establishes connexion over the line L3 and the junction line FL2 over the contacts K3G2. A circuit 10 is then closed through the cut-off relay UR3 and the holding winding HL of the relay AR3. Operation of the relay UR3 opens the circuit of the marking and group relays MR3 and GR3, and disconnects the testing apparatus S. The marking of two simultaneous calls in the same group may be prevented by any known method. In the arrangement shown, the current through two parallel windings of marking relays will not keep two armatures attracted. As the self-induction for two relays is never exactly the same, one will release its armature before the other, and reenergizing, will operate the group relay to open its contact before the other can close its circuit. In the arrangement shown in Fig. 3, simultaneous calls in the same group are prevented by arranging the corresponding marking relays of different groups G in further secondary groups SG, each of which is provided with a secondary group relay SGR. If two or more calls occur simultaneously in the same group G, i.e. in different groups SG, only one of the secondary group relays SGR can remain in its operated position and only the corresponding line is therefore marked as calling.