Patent GB-737509-A (GB)
Title: Improvements in or relating to switching arrangements for automatic telephone systems
IPC: H04Q3/00
Filed: 1953-05-18
Abstract: 737,509. Automatic exchange systems. TELEFONAKTIEBOLAGET L. M. ERICSSON. May 18, 1953 [May 16, 1952], No. 13911/53. Class 40 (4). In a cross-bar group selector using 10 x 12 primary and secondary switches, gas-discharge tubes are used to select a free secondary outlet in a wanted group and a free link to interconnect the calling line and the selected outlet. The cross-bars are doubled. Each of the ten inlets of a switch has access to two sets of 10 outlets discrimination being provided by two auxiliary select magnets. The gas discharge tubes include auxiliary electrodes forming three discharge paths which are controlled by the links and secondary outlets. A tube cannot strike to make a connection through the selector unless the associated link and outlet are free and two corresponding discharge paths have been made conductive. A calling line bypasses the primary switch proper, but is connected to a register over contacts controlled by a select magnet of the primary switch. General arrangement, Fig. 1. Primary switches K1, K2 and corresponding secondary switches K11, K21, and K12, K22 are interconnected by links m1, m2, &c. and are controlled by a marker M1 individual to the group selector. Only the marker M2 and switches K3, K13, K23 of a second group selector are shown. Both selectors have access to lines L1, L2. Selection of line in wanted group, Figs. 2, 3. A calling line FL strikes the auxiliary gap (1, 2) of tube F1 (the cathode being numbered 1) and triggers FA in the marker. Relays B, BA follow. Select magnet H11 and relay G1 operate in series over contacts 22, 32 as the auxiliary gap (3, 2) strikes on F1. Magnet H11 is not effective in the switch K1 but it connects the line F1 over wires a, b to a register MM into which the wanted number is dialled. Relay A1 operated when Fl (3, 2) struck and triggered FB1. Relays A1, G1, FB1, R1 and A2, G2, FB2, R2 correspond to primary switches K1 and K2 respectively. The register operates relay Wn to mark the wanted group of lines. There are forty secondary outlets in each group available to a single calling line and forty tubes TR1 ... TR40 are connected to them by A1 to select an idle one. In tube TR1, for example, the gap (1, 2) strikes over contacts 100, 131 indicating that link m1 is free. Gap (2, 3) of TR1 strikes over resistor r10 and contacts 150, 113 indicating that the outlet to L1 is free in the wanted group, in switch K21, to which link m1 is connected. All tubes TR1-TR40 associated with a free link and a free line in the wanted group are now conducting in gaps (1, 2, 3). The potential on contact 116 tends to strike over gap (3, 4) in each of these tubes, but resistor r8 ensures that only one tube, say TR1, strikes and makes the necessary selection. The main gap in TR1 follows over contact 115 and relay T1 operates the switches K1, K21. Operation of switches K1, K21. In switch K21 select magnets HA2, H20 operate in series over contact 121 of T1. Relay MT10 follows T1 and select magnets HA1, H10 in K1 operate in series with operating magnet V21 in K21 over the gap (1, 3) in tube R1 which was primed when FB1 struck. The main gap (3, 4) in tube F1 fires and magnet V1 in switch K1 operates in series with relay P which releases the marker M1. All the discharge tubes are extinguished. Operating magnets V1, V21 are held over conductors c1, c2.