GB666445A - Improvements in control circuits for use in automatic exchange systems - Google Patents

Abstract

666,445. Automatic signalling systems. NAAMLOOZE VENNOOTSCHAP PHILIPS' GLOEILAMPENFABRIEKEN. Sept. 8, 1949 [Sept. 11, 1948], No. 23280/49. Class 40 (iv). A wiper e moves over contacts e<SP>1</SP> corresponding to communication channels, contacts marked as free channels having a direct voltage potential algebraically lower than that of contacts corresponding to busy channels; the wiper is connected to the cathode of a valve B5 cross-coupled to a valve B6, so that when one is conducting, the other is non-conducting; when the wiper d which is ganged with e reaches the position corresponding to wiper MS a high potential is applied from OI which, if the wiper e is on a contact corresponding to a free channel, causes valve B5 to conduct and valve B6 to cease conducting so as to release relay SM and stop the wipers d, e; but if the wiper e is on a contact corresponding to a busy channel, valve B5 does not conduct; when valve B5 conducts, the wiper is brought to the potential corresponding to a busy condition. The invention is described with reference to the system described in Specification 662,215, [Group XL (c)], in which a wiper MS is positioned in response to a numerical criterion on one of a series of contacts having different potentials and a further wiper d is stepped on over a further series of contacts having different potentials until it finds one having the same potential as the one marked by MS, when valve B4 is rendered non-conducting to stop wiper d. Preferably the relay SM is in the anode circuit of a valve B7 whose grid is directly connected to the grid of valve B6.