| 摘要 |
1,055,434. Automatic exchange systems. SIEMENS & HALSKE A.G. Oct. 4, 1963 [Oct. 5, 1962], No. 39156/63. Heading H4K. A scanning system for detecting the presence of metering pulses in subscribers' line circuits comprises a metering-pulse generator which applies pulses to the input of respective bistable circuits the outputs of which are connected to the lines of subscribers engaged in a call and a line scanning circuit the duration of the scanning cycle of which is greater than the duration of a metering pulse but less than the interval between two metering pulses and wherein a change in state of the bi-stable circuit between two successive line scans is interpreted as a metering pulse. The system is applicable to a large exchange having centralized metering arrangements using relatively slowly moving rotating memories AE, e.g. magnetic drums or ferrite core stores. With such arrangements the possibility exists that a metering pulse provided by generator Zi via connector RSA to a line circuit TS will be lost because the scanning cycle of the drum is longer than the duration of a metering pulse. This drawback is overcome by the insertion of the bi-stable circuit BS in the metering path. The capacity of the system may be increased or alternatively the scanning speed may be reduced if, instead of the lines, the outputs of the bi-stable circuits are scanned directly. |
