Northern Telecom Limited

C-i-l, Inc.

Jerzy Borkowicz

James E Anderson

William P Trumble

Robin McIntyre

Frederick Caldwell Livermore

A solid-state surge protection device comprises a semiconductor chip sandwiched between two electrodes. A resilient sealing member or layer comprised of a thermoplastic or thermosetting resin extends around the periphery of the device, adhering to both electrodes, so as to seal the interface region between the chip and each electrode. The resin is a flexible, dielectric material which is not disrupted by heat generated under surge conditions in the device, is environmentally inert, and preferably remains compliant under extremely cold conditions. The electrodes of the device can move together into electric-conductive contact in the event of chip destruction, or can move back into contact with the chip if separated therefrom by an arc.

Packaged solid-state surge protector

A solid-state surge protection device comprises a semiconductor chip sandwiched between two electrodes. A resilient sealing member or layer comprised of a thermoplastic or thermosetting resin extends around the periphery of the device, adhering to both electrodes, so as to seal the interface region between the chip and each electrode. The resin is a flexible, dielectric material which is not disrupted by heat generated under surge conditions in the device, is environmentally inert, and preferably remains compliant under exteremely cold conditions. The electrodes of the device can move together into electric-conductive contact in the event of chip destruction, or can move back into contact with the chip if separated therefrom by an arc.

A two-wire telephone subscriber line protection arrangement consists of two protection devices each comprising a pair of complementary thyristors connected in reverse parallel with one another between a respective wire and a reference point, with their gates connected together and directly to a control terminal which has a connection to the wire via a resistance which determines an overcurrent threshold level for the device. The reference point is ground for the ring wire protection device, and is desirably the ring wire for the tip wire protection device, whereby a directional sensitivity of the protection devices is taken advantage of and the overcurrent threshold level can be reduced. Zener diodes connected between complementary thyristors provide for convenient overvoltage protection.

Protection devices and arrangements for telephone lines

A solid state switching device allows independent control of the latching and holding currents, and has particular application to telephone systems. The holding current may be set at a high level so as to return the switching device to the off-state without a large reduction in the current to the circuit embodying the switching device, whereas the latching current may be set at a low level to reduce the heat dissipation in the device just prior to the transition from the latching state to the holding state. The device, which may be implemented in either linear technology or with discrete components, is a thyristor structure defined by npn and pnp bipolar transistor devices each having its base connected to the collector of the other. Each transistor device has a resistance between its base and emitter, and in the case of at least one of the transistor devices that resistance varies with the voltage on the collector of the associated transistor device.

Solid state switching device

A five layer two electrode semiconductor switching device which provides bi-directional overvoltage protection. The device is constructed so that relatively high holding currents are achieved without substantially altering its turn-on switching time, or its power handling capabilities. This is achieved by providing a shorting junction along both sides of the outer diffused regions of the device thereby substantially reducing its resistance when conducting.

Bi-directional overvoltage protection device

An apparatus and method is provided for measuring the continuity and resistance of electric circuits, particularly electric wire circuits used in blasting, in the presence of spurious voltages due to galvanic currents. A constant current from a cell is passed through the electric circuit to be tested and through a reference resistor where the voltages are measured to derive the resistance of the circuit. The measured voltages are sensed with a converter converted to a resistance measurement and displayed. The presence of spurious voltages is compensated for by connecting a galvanic current storage capacitor in the circuit, passing a reference current through the reference resistor and the circuit and comparing the voltage across the reference resistor with the voltage across the circuit and storage capacitor to derive a resistance reading. The reading is converted to a digital display. The method and apparatus provides a quick, convenient means of testing blasting circuit continuity in the field in the presence of stray current caused by in-earth galvanic action.

Digital display ohmmeter

An overvoltage protection device, especially for telephone equipment and the like, comprises two protectors connected directly in parallel. One protector, for example a back-to-back semiconductor diode, has a breakdown voltage below which it is a high impedance. Between the breakdown voltage and a failure voltage it has a lower impedance. Above the failure voltage it has negligible impedance. The other protector, for example a gas tube, has a range of operating voltages which extends from below the breakdown voltage of the diode, to a voltage between the breakdown voltage and the failure voltage of the diode. In operation the two protectors interact, the diode operating, for example, on faster surges and, in so doing, slowing the surge front so as to increase the likelihood that the gas tube will fire.

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Ottawa, Canada

Jerzy Borkowicz