GB542081A - Improvements in or relating to mechanism-selecting circuits - Google Patents

Abstract

542,081. Automatic exchange systems. ELECTRICAL RESEARCH PRODUCTS, Inc. May 24, 1940, No. 9179. Convention date, July 11, 1939. [Class 40 (iv)] An allotting circuit such as the starting circuit of a call finder comprises a number of threeelectrode neon &c. tubes 152, 154 &c., one for each finder &c., each associated as shown with a pair of resistances 113, 115 in a chain circuit and with a condenser 151. When, as the result of a demand for a finder &c., a break-down potential is applied by a sub-group starting relay such as 100, 156 to the left-hand end of a section of the chain, the potential builds up to the right from this point until it reaches the tube of an idle finder. This tube breaks down to start its finder and so lowers the potential that no other tube responds. When the callfinder switches through, it disconnects the cathode of its tube and releases the starting relay. In the arrangement shown, each section of the chain corresponds to a level in a group of double-wiper finders. Assuming tube 152 to breakdown, its relay 102 causes the finder vertical magnet 109 to interact with relay 167 until the vertical wiper 112 finds the terminal marked by the starting relay, whereupon 176 pulls up in series with 167 which thus remains operated. Relay 168, which has remained operated during vertical stepping, now falls and energizes the rotary magnet. Vertical wiper 112 moves off the bank 170 at the first step. If neither of the lines in the first position is calling, wiper-changing relay 169, which operated and locked at the end of the vertical movement, is held over wiper 122. 167 which was released by the rotary magnet therefore pulls up again over wiper 130 and the rotary magnet is re-operated. This interaction continues until the calling position is reached whereupon 169 falls if the calling line is reached over the lower set of wipers. In any case no circuit is made for 167 and switching relay 153 being no longer short-circuited pulls up in series with 167 and holds 169 if the calling line is reached over the upper set of wipers. 153 also disconnects the cathode of the discharge tube to release 102 and energizes the cut-off relay.