Abstract: Methods and circuits are provided for monitoring a battery with the monitored battery electrically connected in an operating system. A dynamic impedance characteristic of the monitored battery is identified and compared with a predefined value. An alarm signal is generated responsive to the compared values to predict a degraded battery capacity. A leakage current value through the monitored battery is detected. An alarm signal is generated responsive to the detected leakage current value to predict a short life expectancy for the monitored battery. Visual and audible alarms are generated responsive to either of the generated alarm signals after the monitored battery has been fully charged. An alarm signal is immediately generated responsive to a detected charging current value above a predetermined value.

Abstract: A surge/transient protector for an N-line data cable (e.g., N=16) or other group of N data lines having two data conductors and a return conductor for each line includes individual conductor segments for each data line conductor; conventional multi-pin connectors are used to connect the protector in series in the lines. The protector has a positive bus, a negative bus, and a ground bus; each data conductor segment is coupled by a pair of oppositely polarized diodes to the positive and negative buses, and each return conductor is coupled to the reference bus by two oppositely connected diodes. Two large capacity energy storage devices (e.g. 10,000 microfarad capacitors) are connected between the reference bus and the positive and negative buses, each paralleled by a Zener diode to establish a discharging threshold just slightly greater than one-half the voltage range for the data lines.

Abstract: A protection circuit is provided for a tap switching line voltage regulator of the type which selectively switches in one of a predetermined number of taps on a winding of a transformer. The selective switching of the taps is controlled in response to the sensed load voltage to provide a regulated voltage to a load in the presence of a varying input line voltage. The tap switching line voltage regulator in response to the sensed load voltage controls the conductive state of a solid state series switching element in each of the switched tap lines. The protection circuit provides current limiting inductors in series with each of the solid state switching elements with all the inductors being wound on a common magnetic core. When switching from one tap to another tap, the tap switching line volage regulator in response to the sensed voltage operates to select an adjacent tap to the tap currently selected. Thus, tap switching proceeds in a sequential fashion up and down along the taps.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.