Oneac Corporation

Teradyne, Inc.

Corcom, Inc.

Thomas McCartney

Melvin A Lace

Andrew McCartney

Michael P Raleigh

Glynn R Ashdown

August G Klingbiel

Robert T Thomas

Laurence H Fish

Bruce Holmes

A method and apparatus are provided for protecting a pair of telephone lines and similar data communication channels from overvoltage and transients. A filter for filtering noise and transient voltage signals above desired data signals on telephone lines and similar data communication channels includes a longitudinal transformer. The longitudinal transformer includes a single transformer core and a pair of coils. A first one of the coils is connected in series with a first telephone line or a first similar data communication channel. A second one of the coils is connected in series with a second telephone line or a second similar data communication channel. The pair of coils are substantially identical; each coil having an identical number of turns. A high impedance is provided with the longitudinal transformer to noise and transient voltage signals above desired data signals. A low impedance is provided with the longitudinal transformer to desired data signals.

Telephone and data overvoltage protection apparatus including a

An external DC (direct current) power supply is provided for supplying backup DC power to a supported device having an AC input connector. The power supply includes an AC (alternating current) voltage source. A voltage rectifier is coupled to the AC voltage source for rectifying the AC voltage source. An energy storage device coupled in parallel to the voltage rectifier provides a predetermined DC voltage threshold level. A connector of the external DC power supply applies a power output of the parallel combination of the voltage rectifier and the energy storage device to the AC input connector of the supported device. The external DC power supply is capable of reliably, effectively and efficiently supplying backup power to the AC power input of a supported system without requiring any special wiring or modification of the supported system using only the AC input plug for connection to the supported system.

External backup power supply

An EMI filter formed with a U-shaped ferrite core with parallel first and second legs and a center leg surrounded by a grounding and shorting strap and a capacitor connected between the grounding and shorting strap and a portion of a conductor which extends between the first and second legs. Two or more of the filters can be formed as a stacked array. The filter has a substantially improved frequency response over the prior art.

Filter formed with a one piece U-shape ferrite core

A method and apparatus are provided for protecting a non-isolated data communications cable against ground skew used with an AC power source. A current summing transformer is coupled to an AC power source. The current summing transformer includes a single transformer core and a plurality of coils. One of the coils is connected in series with each phase, neutral (if present) and ground line in the AC power source. The plurality of coils are substantially identical. Each coil has an identical number of turns and an identical direction of winding on the transformer core. The current summing transformer is only needed in the power path to one of two or more interconnected systems. The current summing transformer introduces a high impedance to surge current in the data cable ground of one or many non-isolated data cables attached to the system and at the same time offers substantially zero impedance to the normal power currents including leakage and fault ground currents.

Ground skew protection method and apparatus

A line noise signal measurement system is provided with detecting circuitry for providing a sensed analog signal. Compression circuitry is coupled to the detecting circuitry for providing an amplitude compressed signal responsive to the applied sensed signal. The compression circuitry has a stepwise substantially linear transfer function responsive to a variable magnitude of the applied sensed signal. Signal processing circuitry is coupled to the compression circuitry for sequentially generating a digital signal representative of the sensed analog signal. Digital processing circuitry sequentially identifies a maximum peak signal for a predetermined time interval and provides linearity correction for the identified maximum peak signals and generates a display of the corrected peak signals.

Line noise signal measurement system using analog signal compression

Overvoltage protection arrangements are provided for a pair of telephone lines effective for suppressing noise and transient voltage signals occurring above data and voice signals carried on the telephone lines and that avoids current flow between the telephone lines responsive to common mode voltage signals on the lines so that audible hum is avoided. The overvoltage protection arrangements include first voltage clamping circuitry for clamping voltage signals on the lines at a first predetermined voltage potential and second voltage clamping and filter circuitry for clamping voltage signals on the lines at a second predetermined voltage potential and for filtering noise and transient signals from the voltage signals only when the voltage signals exceed the second predetermined voltage potential. The second voltage clamping circuitry substantially avoids current flow between the lines responsive to common mode voltage signals on the lines.

Telephone lines overvoltage protection apparatus

Overvoltage protection circuits are provided for coupling a subscriber's station to first and second conductors connected to a telephone system or other similar communications source. The overvoltage protection circuits include first circuitry connected between the first and second conductors for conducting current at a first breakdown voltage and for blocking current below the first breakdown voltage; second circuitry for conducting current at a second breakdown voltage and for blocking current below the second breakdown voltage; and circuitry connected in series between the first and second circuitry for filtering voltage signals on the first and second conductors responsive to the second circuitry conducting current. The overvoltage protection circuits are effective for suppressing noise and transient voltage signals occurring above the data signal and do not require a transient voltage signal to exceed the ring signal for operation.

Telephone and data overvoltage protection apparatus

An AC branch power distribution filter is provided for supplying AC power to a plurality of different load devices from a common external AC power source that eliminates the need for a separate protection device at each power outlet with the load devices. A plurality of elongate, flat conductors are coupled to the AC power source and include a neutral conductor, a ground conductor and at least one live conductor. The elongate flat conductors are parallel and spaced apart in an electrically insulated casing member. An electrically conductive shield member is electrically connected to the ground conductor and extends lengthwise of the elongate flat conductors overlying the insulative casing member. The shield member provides a shunt capacitance between ground potential and each of the live conductors and the neutral conductor. This distributed capacitance is utilized as the shunt element of the distribution filter. Transition filtering circuitry is connected between the plurality of elongate flat conductors and the common external AC power source. The transition filtering circuitry includes an inductance device connected in series with each of the live conductors and the neutral conductor.

AC branch power distribution filter

A dual programmable control time constant circuit is provided for a tap switching line voltage regulator of the type which selectively switches in a sequential adjacent one of a predetermined number of taps on a winding of a transformer. The dual programmable control time constant circuit includes a stepping counter and a first bistable device for determining how long a sensed signal representative of the voltage of the load circuit may be permitted to remain outside preset upper and lower limits before corrective action is taken. A second bistable device is used to reset the stepping counter when the sensed signal has changed so as to again fall within the preset limits for a predetermined time. The dual programmable control time constants provide for large variations in load characteristics with the minimum time required per tap change consistent with stable regulator operation. The surge current caused by excessive tap switching is reduced to prevent damage to the regulator and load components.

Dual programmable response time constants for electronic tap switching

A high voltage filtering and protection circuit that is particularly useful in multilead distribution systems, that include a live, a neutral and a ground line. Transient voltage suppressors are connected from a common node to each of the lines. The suppressors are advantageously silicon diode transient voltage suppressors suitable for high voltage applications, clamping at a rated voltage in one direction and having a forward diode characteristic in the other direction. Each suppressor may be paired with a parallel filter capacitor protected by its diode from surges or transient voltages. The paired suppressors and parallel filter capacitor where polarized capacitors are utilized provides an AC equivalent capacitor. In one arrangement, a gas discharge tube is provided in series with the suppressor that is connected from the common node to the ground line. In another arrangement with or without the gas discharge tube, the suppressors are bidirectional devices with a rated clamping voltage equal to less than the peak line voltage and a predetermined amount greater than one-half of the peak line voltage.

High voltage filtering and protection circuit

An AC variable voltage source utilizing pulse width modulation is provided that converts an input of two AC voltage waveforms of the same frequency but opposite phase into a single AC voltage output of the same frequency but with a variable amplitude. The variable voltage source includes a control voltage input that determines the amplitude of the AC voltage output. The two AC input voltage waveform are provided by buck and boost windings of an AC input transformer having a primary winding connected to an AC source. The variable voltage source utilizes phase switch stages each connected to a respective one of the buck or boost windings and including back to back power MOSFETS. Each of the phase switch stages is controlled at a switching frequence much higher than the AC input frequency with the duty cycle of operation of each of the phase switch stages determining the amplitude of the controlled output. In one arrangement, an inductor is provided in series with each of the phase switch stages for operation in a current fed mode. In another arrangement, an inductor is provided in series with the common output of the phase switch stages for operation in a voltage fed mode. For line regulation of an AC line, the control voltage is a feedback signal derived from the AC regulated output. For a proportional controller, the control voltage is a DC voltage proportional to the amplitude of the desired AC output voltage.

AC Variable voltage source utilizing pulse width modulation

A two-wired telephone testing system employing a low frequency test signal which is a submultiple of the power line frequency. This test signal is applied between the two-wires or between either wire at a point of potential reference (ground). A measure of the integrated value of the current between the connected points is then made for a period equal to one-half cycle of the applied signal with one polarity and one-half cycle with the polarity of the measured signal reversed. The integration periods are selected to be in phase with the applied signal for determining conductance and 90.degree. out of phase for determining susceptance. Direct current measurement can also be made for the same time periods.

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Lake Bluff, IL, United States of America

Thomas McCartney