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Abstract

A telephone interconnect detection system for selectively determining, during operation, interconnection of a plurality of trunk lines with a plurality of set lines interconnected by a pbx or the like. The system includes a processor for selecting in sequential order ones of the trunk lines according to a predetermined logic, and generating trunk and set operation control signals; a pulse generator for generating a limited bandwidth and duration sensing pulse within the audio bandwidth of the pbx; a multiplexer for selectively applying one of the sensing pulses to one or more selected trunk lines for transmission of the pulse through the pbx; a selectively operable band-reject filter connected to the trunk lines and tuned to the frequency of the sensing pulse, the filter operating in response to the trunk operation signal to attenuate the pulse for inhibiting its outbound transmission over the trunk lines; a detector connected to the set lines for detecting the presence of the sensing pulse on any one or more of the set lines, and identifying those one or more set lines; and a selectively operable second band-reject filter connected to the set lines and tuned to the frequency of the sensing pulse, the filter operating in response to the set operation signal to attenuate the sensing pulse for inhibiting its outbound transmission over the set lines. The first and second filters include a plurality of individual two stage filters, one filter being connected to each of the trunk and set lines.

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