Abstract: Telecommunications conductor wire pair test circuits are provided. The test circuits include a switch electrically coupled to the wire pair. The switch has a first position in which the test circuit provides an open circuit across the wires of the wire pair and a second position in which the test circuit is detectable across the wires of the wire pair. An energy storage cell is electrically coupled across the wires of the wire pair so as to charge the energy storage cell when the switch is in the second position. The switch is powered by the energy storage cell. An energy monitor circuit is electrically coupled to the energy storage cell which detects an energy level of the energy storage cell. A switch control circuit switches the switch from the first position to the second position responsive to the energy monitor circuit. In other embodiments, the switch is a relay and the energy monitor circuit is optionally included. Methods are also provided using the test circuit.

Abstract: An overvoltage protection device includes a housing including a first substantially planar electrical contact surface and a sidewall. The housing defines a cavity therein and has an opening in communication with the cavity. An electrode member of the device includes a second substantially planar electrical contact surface facing the first electrical contact surface and disposed within the cavity. A portion of the electrode member extends out of the cavity and through the opening. A wafer formed of varistor material and having first and second opposed, substantially planar wafer surfaces is positioned within the cavity and between the first and second electrical contact surfaces with the first and second wafer surfaces engaging the first and second electrical contact surfaces, respectively.

Abstract: An overcurrent protection arrangement comprises a switching circuit that is intended to be series connected in a line of the circuit to be protected and which will allow normal circuit currents to pass but will open when subjected to an overcurrent. The arrangement includes a pulse generator which will generate pulses when the switching circuit has opened that reset, or attempt to reset, the switching circuit to its conducting state. Only a predetermined finite number of pulses or pulses for a predetermined finite time are generated, so that the circuit will quickly function again after having been subjected to a current transient but will not continually attempt to reset in the case of equipment faults.

Abstract: A two terminal circuit protection arrangement that: (1) is intended to be series connected in a line of the circuit; (2) comprises (a) a series switching transistor (1) that controls the line current, (b) a control transistor (4) that controls the base or gate voltage of the switching transistor and is responsive to an overcurrent through the switching transistor, and (c) a voltage source, for example a battery (3), a dc-dc converter (58/59) or a Seebeck device (43), applied to the base or gate of the switching transistor which biases the switching transistor into or toward conduction in normal operation; and (3) is capable of being remotely reset into a conducting state by stopping current in the line. The arrangement enables the initial voltage drop that is required to turn the switching transistor (1) on to be reduced or eliminated while requiring relatively little current from the voltage source. The arrangement can be reset remotely by briefly removing the voltage source or load from the circuit.

Abstract: An overvoltage protection device includes a first electrode member having a first substantially planar contact surface and a second electrode member having a second substantially planar contact surface facing the first contact surface. A wafer formed of varistor material and having first and second opposed, substantially planar wafer surfaces is positioned between the first and second contact surfaces with the first and second wafer surfaces engaging the first and second contact surfaces, respectively. The contact surfaces may apply a load to the wafer surfaces. Preferably, the electrode members have a combined thermal mass which is substantially greater than a thermal mass of the wafer. The wafer may be formed by slicing a rod of varistor material. The device may include a housing including the first substantially planar contact surface and a sidewall, the housing defining a cavity within which the second electrode is disposed.

Abstract: An arrangement for protecting an electrical circuit such as a telephone circuit from a voltage transient comprises a voltage clamp or foldback device (3) arranged to be connected between a current-carrying line (1) and ground (1'), a capacitor (2) in series with it, and an inductance (4) series connected in the line. During normal operation the arrangement acts as an LC filter whose high frequency break-point is determined by the capacitance of the voltage clamp or foldback device (3) and the value of the inductance (4) which are chosen to give a break point of 1 kHz to 10 MHz. However, when the arrangement is subjected to a voltage transient, the voltage clamp or foldback device (3) fires causing the break-point to fall to a value determined by the values of the capacitor (2) and inductance (4). The arrangement may be used, for example, to protect the circuit against a rapid voltage drop caused by the firing of another circuit protection device such as a gas discharge tube 5.