Patent GB-187580-A (GB)
Abstract: 187,580. Relay Automatic Telephone Co., Ltd., (Assignees of Betulander, G. A.). Oct. 15, 1921, [Convention date]. Automatic exchange systems and apparatus: selectors.-In cross-bar switching arrangements for connecting an incoming line G1, Fig. 3, to an idle outgoing trunk G2, each outgoing trunk is multipled to all or a proportion of the contact sets KG at the points of intersection of the vertical and horizontal rows of a cross-bar switch RV. In the arrangement shown in Fig. 3, each outgoing trunk G2 is multipled to all the contact sets KG of a separate switch RV and each incoming line G1 is connected to a single contact set in each switch, whilst in a modified arrangement, Fig. 4, each outgoing trunk G2 is multipled to half the contact sets of a switch RV, each incoming line G, being connected to two contact sets in each switch. The operation of an arrangement similar to that shown in Fig. 3 is described in greater detail with reference to Fig. 5, in which are diagramatically indicated two contact sets of two vertical rows of each of two switches RVI, RV2 for connecting a calling line such as AL1 to an idle outgoing trunk such as FL1 over a contact set KG1 at the point of intersection of a vertical row, mechanically marked by the energization of a marking relay MR1 and a horizontal row indicated by the response of a connecting relay AR1, the relays AR1, MR1 being controlled by a common searcher RS. Upon a call occurring, for example, on the line AL1, the response of the line relay LR1 closes a circuit 2 for the test relays PR1, PR2 of the searcher, so that the test relays of idle trunks are energized over contacts k1, k3. The test relay of the first idle trunk (say FL,) opens the circuits of the succeeding test relays and energizes a group relay GR1 of the first switch RV1, the last mentioned relay locking up and closing a circuit for a switching relay OR1, which connects up a parallel switching relay OR2. The circuits of the test relays PR1, PR2 are now transferred at contacts k4 to vertical row test wires RL, earth at a contact 5 of the line relay LR1 causing the relay PR1 to again energize. Simultaneous calls in different vertical rows over, for example, lines AL1, AL12, are prevented at this stage since the energization of the test relay PR1 cuts out the test relay PR2. A circuit 6 is now closed for the first vertical row marking relay MR1 of the first switch RV1, over contacts of the group relay GR1. (If the first trunk FL, had been engaged the circuit 6 would have extended to the first vertical row marking relay of the second switch RV2 over contacts of the group relav GR2). Relay MR1 locks up in a circuit 7 in which responds the switching relay OR3, which cuts in the parallel relay OR4, and at contact k5 transfers the circuits of the test relays PR1, PR2 to the test wires SL, and since the first incoming line AL1 in the first vertical row is calling relay PR, responds in a circuit 8. If simultaneous calls occur in the same vertical row, a branch of the circuit 8 also extends over test relay PR2, but the response of the test relay PR, prevents its energization. The lower winding AL of the first connecting relay AR1 now energizes in series with a switching relay SR over a circuit 9, the contacts KG1 at the point of intersection of the horizontal and vertical members being operated to connect the calling line AL1 to the trunk FL1. The energization of a relay FR1 over the calling loop, completes a holding circuit 11 for the connecting relay AR1 over its upper winding HL and energizes the cut-off relay UR1, which disconnects the line relay LR1. The switching relay SR closes a circuit for a relay TR1 which cuts in a parallel relay TR2, thereby causing the relapse of relays PR1, GR1, MR1 and all the switching relays OR1, TR1, &c. In a modified arrangement, Fig. 6, the common searcher RS is dispensed with by inserting the. marking relays MR directly in the outgoing trunk test circuits and causing them to mutually control their own circuits. On a call occurring over the line AL1, a circuit such as 13 is closed for a common relay RR and for the first marking relays MR1 of all the switches associated with idle outgoing trunks. If the first trunk FL1 is idle, the response of the first marking relay MR1 of the switch RV1 cuts out the other marking relays, and completes a circuit 14 for the first connecting relays AR1 of idle switches. A connection is only effected however in the switch RV1, since this is the only switch in which a marking relay is energized. The connecting relay AR1 locks up over its upper winding in series with the cut-off relay UR1 which disconnects the line relay LR1. Simultaneous calls in the same vertical row, say over lines AL1, AL2, are prevented since the line relay LR1 opens the circuit of the connecting relay AR2. The same result might be attained by making the line relays of incoming lines connected to the same vertical rows, mutually control each others circuits. If simultaneous calls are received in different vertical rows, say over lines AL1, AL12 only the marking relay MR2 of the second vertical row will operate, since at contact k<8> the marking relay MR2 cuts out the marking relay MR1. A construction of cross-bar switch is referred to in which each vertical rod of a switch may be set in any one of several positions to operate the contact sets of several vertical rows.