Improvements in or relating to an electronic selection control circuit having a device for determining the null point for effecting selection

摘要

918,036. Automatic exchange systems. SIEMENS & HALSKE A.G. Sept. 15, 1960 [Sept. 17, 1959], No. 31884/60. Addition to 888,196. Class 40 (4). In a selection control arrangement, for marking an idle one of a number of circuits, consisting of a number of stages each associated with one of the circuits, each stage has a marking output at which marking potential appears only when " free " potential is applied to its testing input and " release " potential to its coupling input, and a coupling output at which " blocking " potential appears when marking potential appears at the marking output, or when " blocking " potential is applied to the coupling input, the arrangement being such that the blocking potential appears at the coupling output without time lag, the connection between the coupling input and coupling output of each stage is established by a transistor and the stage at which an attempt at selection is to be commenced is determined by connecting a further potential to an auxiliary input of that stage which input is connected to the coupling output of the respective stage. Each of the stages A, B ... N may be in accordance with any of the stages disclosed in the parent Specification which has a transistor connected between its coupling input k1 and its coupling output k2. The auxiliary input n is connected to k2 over rectifier G1 and to the base of the transistor over G2, and the stages are connected in a closed ring. A device Sp connects positive potential corresponding to the release or idle potential to input n of one stage and a negative potential corresponding to the blocking potential to the others. In the one stage the positive potential appears at k2, and hence at k1 of the succeeding stage, which is thus the first choice stage. This potential also disables the transistor of the one stage.