Lucent Technologies Inc.

At+t Corp.

Agere Systems Guardian Corp.

Dean Michael Umberger

Dewayne Alan Spires

Craig Brian Ziemer

David P Chabinec

An integrated ringing access switch circuit for telecommunications switching applications that provides improved dV/dt sensitivity at low operating power by using a pilot controlled rectifier, such as an SCR, that conducts at low ringing signal currents and operates to steer a bias current for causing a relatively larger controlled rectifier in parallel therewith to become conductive during higher load current operation. Also included is circuitry for preventing inadvertent turn-on of the SCRs in response to transient signals.

Low operating power, high voltage ringing switch circuit

The present invention is directed to an integrated circuit comprising a voltage source and a voltage sensing circuit having a switch circuit for sensing a switch voltage and a switch current; a voltage comparison circuit connected to the switch circuit for comparing the switch voltage to a limiting voltage; and a current limiting circuit connected to the switch circuit and the voltage comparison circuit, which is capable of limiting the switch current when the switch voltage reaches or exceeds the limiting voltage. In a preferred embodiment of the invention the switch circuit is a bi-directional switch circuit and the voltage comparison circuit incorporates a series of Zener diodes, wherein the current limiting circuit is a current foldback circuit.

Voltage sensing current foldback switch circuit

An overvoltage protection circuit using a diode bridge and a thyristor. The inputs to the bridge (first and second terminals) are coupled to a telephone line to be protected. The positive output of the bridge connects to a ground while the negative output of the bridge (intermediate node) connects through a thyristor to the ground. The thyristor is triggered into conduction when the voltage on the negative output of the bridge exceeds a reference voltage. The reference voltage is preferably the battery voltage for the telephone line.

Overvoltage protector

A high sensitivity control circuit for a solid-state relay is disclosed for use in optically coupled solid state relay circuits having a light emitting diode. The control circuit reduces a loading effect of the turn-off circuit on a photodiode array allowing the photodiode array to operate the switching transistor to switch an input signal to a switching contact. A two stage CMOS transistor circuit acting as an amplifier is employed for high-speed switching. Deactivation of the light emitting diode reverse biases a sense photodiode to discharge the switching transistor to prevent switching of the input signal to the switching contact.

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Stouchsburg, PA, United States of America

Dean Michael Umberger