Fujitsu Network Communications, Inc.

Mark Bolla

Serdar Kiykioglu

Tsuyoshi Ueshima

Peter Vaclavik

A ring trip detector has a voltage difference detector with first and second inputs, for supplying an off-hook signal upon detection of a voltage difference. The ring trip detector also has a switch extending between the first and second inputs of the voltage difference detector. The ring trip detector detects when a telephone current starts to flow through a sensing resistor having first and second ends and to a telephone set. The switch closes upon an initial current flow through the sensing resistor and then opens. The ring trip detector has a pulse generating mechanism having two inputs respectively connected to the first and second ends of the sensing resistor. The pulse generating mechanism has an output and generates a pulse at the output when current starts to flow through the sensing resistor. The switch has a trigger connected to the output of the pulse generating mechanism for closing the switch when the pulse is generated. A differentiator mechanism may be used as the pulse generating mechanism. Such a differentiator mechanism may have a resistor and a capacitor connected in series between the first end of the sensing resistor and the trigger of the switch, and a resistor connected between the second input of the voltage difference detector and the trigger of the switch. Alternatively, a differentiator/integrator mechanism may be used as the pulse generating mechanism.

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Richardson, TX, United States of America

Mark Bolla