Mitel Corporation

Brian J Vaughan

Brian J Pascas

A dial pulse detection circuit for partial correction of grossly distorted line current dial pulses, which provides square wave output signals for use by later timing detection circuitry. To detect such dial pulses, the present invention establishes an upper and a lower detection threshold. For a valid dial pulse to be detected, the line current must drop through both thresholds, and then rise again through at least the lower threshold. With the provision of a detection delay following detection of the leading edge of a dial pulse, the presence of a valid dial pulse can be registered. The present technique used in detecting the presence of dial pulses substantially reduces the chances of rejection of a valid dial pulse which has a grossly distorted waveform.

Dial pulse detector

A circuit for translating a loop start to a ground start signal in a communication system interconnected via a tip lead and a ring lead, in which the ring lead is connected to a source of potential at a central office or PABX, is comprised of a latching switch connected from a ring lead terminal through a resistance to a ground terminal, a latching switch closing circuit connected to the tip lead for sensing a predetermined potential applied thereto, adapted to close the switch upon its detection of at least a predetermined proportion of the potential applied to the tip lead as a result of the external application of the source of potential from the ring lead to ground, and a latching switch opening circuit adapted to open the switch following connection of the tip lead to ground through external circuity at the central office or PBX.

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Ottawa, Canada

Brian J Vaughan