Patent GB-542827-A (GB)
Title: Improvements in or relating to telephone exchange systems
IPC: H04Q11/04
Filed: 1941-01-20
Abstract: 542,827. Automatic exchange systems. ELECTRICAL RESEARCH PRODUCTS, Inc. Jan. 20, 1941, No. 764. Convention date, Jan. 23, 1940. [Class 40 (iv)] [Also in Group XL] In a system in which an idle trunk in the proper direction is selected by a common marker, the trunks are represented by a bank of lamps 100, those corresponding to idle trunks being lighted, and the lamps are focussed on the photo-electric screen 113 of an iconoscope 111 so as to be scanned by a cathode beam having both horizontal and vertical movement, for example as described in U.S.A. Specification 2,178,464. The invention is applied to the system described in Specification 530,085, in which a marker taken into use by a sender 107 receives the dialled exchange digits therefrom and translates these digits to operate a route relay 201-204 identifying a group of outgoing junctions. The bank 100 which may comprise 2500 lamps is common to a number of iconoscopes, each individual to a marker. The output of the iconoscope includes an amplifier 110 which can be effective only when both wires 114, 115 are connected to positive potential. A pair of cathode ray tubes 450, 451 of the kind described in Specification 539,315, [Group XL], in which the beam rotates under the influence of a revolving magnetic field apply positive potential in succession to 50 anodes, and the beams of the two tubes rotate in synchronism with the vertical and horizontal movements respectively of the scanning beam of the iconoscope 111. The anodes are connected to terminal blocks 210, 211, which are in turn cross-connected to groups of four terminals on a block 212, each group corresponding to a route relay 201-204. The two inner terminals 216, 214 serve to extend positive to wire 114 while the beam is scanning the horizontal row or rows of lamps containing the wanted group. The two outer terminals 215, 213 serve to extend positive impulses to control a pair of discharge tubes 224, 221, which are coupled by a condenser 223 so that the discharge of either stops that of the other. The start impulse over terminal 215 starts the discharge of the tube 224, thus applying positive to wire 115, and the stop impulse over terminal 213 stops this discharge by starting that of the tube 221. The amplifier 110 therefore can be operative only while the lamps of the wanted group are scanned. If no lighted lamp is found, relay 228 operates in the output of the tube 221 and connects up busy relay 231. To identify a lighted lamp, the output of the amplifier 110 is applied to the control grids 303, 304 of a pair of tubes 300, 301 similar to and operating synchronously with 450, 451, but normally biassed to suppress the beam. The anodes are connected to two groups of 50 cold cathode tubes 308, 358, the output circuits of which pass through the vertical and horizontal windings of a crosscoil switch 350 of the kind described in U.S.A. Specification 2,187,115 in series with relay 302. When a lighted lamp is encountered, the tubes 300, 301 strike followed by a tube in each of the groups 308, 358, and the switch 350 closes contacts to identify the idle junction. Relay 302 pulls up, disconnecting busy relay 231 and generating in its lower winding an impulse which causes the tube 221 to discharge instead of the tube 224, thus disabling the amplifier. Instead of employing the tubes 450, 451 to control the condition of the amplifier 110, a route relay such as 170 might close the circuits for only those lamps that are included in the wanted group.