GB1348604A - Telephone subscribers metering arrangement - Google Patents

Abstract

1348604 Automatic exchange systems INTERNATIONAL STANDARD ELECTRIC CORP 27 April 1972 [29 April 1971 (3)] 19625/72 Heading H4K In a telephone metering arrangement, each subscriber's line is provided with a respective electronic (i.e. static electrical) gate that is scanned at a rate high enough not to miss any metering pulse by a scanner that is duplicated in its entirety. The arrangement is applicable to exchanges using rotary or cross-bar switches. As shown, a group of 16 subscribers' gates are connected between a common duplicated enabling amplifier AMP1, AMP2 and respective duplicated transistor discriminating amplifiers. The latter are effective to discriminate genuine metering pulses from impulsive interference having voltages up to 50 v., durations of 15 m.sec. and frequencies up to 6 Hz. The outputs B of each amplifier pair are individually connected to a data processor which distinguishes the members of a group by virtue of the individual connections and also ensures that all metering pulses are registered once and only once. The gates, which are not duplicated, each consist of a resistor chain R1, R2 and R3 connected between a subscriber's C wire and a reference potential e.g. earth. Resistors R1 and capacitors C1 form a filter for giving additional protection against impulsive noise. An output from each gate is taken from the junction of resistors R2, R3 via a diode D1 to the discrimination amplifiers. An input to each gate extends over capacitor C2 from the scanning amplifiers AMP such that if a metering pulse is present when a scanning pulse appears the potential change at the junction of R2, R3 is effective on the discrimination amplifier. The group scanning amplifiers are driven by respective crosspoint gates in a duplicated matrix which is scanned by a duplicated, 10-stage binary counter stepped at a 10 kHz rate by 8 Á sec. pulses from a duplicated clock. The outputs of the clocks, the counters and the scanning amplifiers are all connected to fault detection circuitry. All the circuits are made up in integrated circuit format.