At&t Information Systems Inc.

Bell Telephone Laboratories

American Telephone and Telegraph, Co.

At+t Corp.

Richard J Cubbison, Jr

A non-invasive directional coupler (51) comprising a voltage probe (300) and a current probe (301) is used to detect and separate from each other digital pulses (quats) being transmitted in opposite directions on a digital ISDN subscriber loop 200 (U-interface 15). The voltage probe measures the sum of digital pulse voltage of the conductors (201, 202) of the loop while the current probe measures the difference of digital pulse currents of in the conductors. An equalizer (304) converts the difference of the currents into the difference of the corresponding voltages. The sum and difference voltage measurements are then added (305) and subtracted (306) respectively to obtain voltages for digital pulses propagating in each direction. The voltages are provided to a decoder (52) such as a protocol analyzer for processing to interpret the traffic being sent in each direction on the loop.

Non-invasive link monitor

The cordless static electric discharge unit for discharging static electricity from a human body into the air. The apparatus consists of a discharge unit attached to the wearer's wrist by a wrist strap. The discharge unit utilizes a radioactive source to ionize air and the flow of the ions discharges the human body. If the human body is at a positive potential with respect to ground, the negative ions flow to the human body whereas the positive ions flow from the discharge unit to a grounding point. The discharge unit is mechanically constructed such that sub-atomic particles emitted by the radioactive material are prevented from entering the human body or flowing into the surrounding air.

Static electric discharge apparatus

Apparatus for discharging static electricity from the human body by ionizing air and utilizing the flow of ions from the apparatus into the surrounding environment to discharge the body. The apparatus utilizes two power supplies to raise two embedded electrodes positioned in a horizontal plane different voltage potentials with respect to the body. The air is ionized by utilizing discharge electrodes of the opposite polarity positioned over each of the embedded electrodes which results in air ions being formed in a ion distribution above each embedded electrode. The embedded electrodes are positioned a predetermined distance from each other in the embedded plane. Within the region between the embedded electrodes, the ions recombine to form air molecules. The ions in the distribution layers above each embedded electrode drift toward this region under attraction from each other. As the ions move, ions of the same polarity as the body as repelled into free air by virtue of the presence of the static charge on the body. In free air, they eventually drift to a grounding point within the environment. This expulsion of the ions of the same polarity as the body discharges the static electricity from the body.

Static electric discharge apparatus with active electrical circuit

Battery feed circuits function to supply a predetermined current to the communication pair and include circuitry to counteract the effects of balanced longitudinal signals which appear on the communication pair. Prior art battery feed circuits use either expensive matched power resistors or matched and tracking current sources to provide both the dc current and the necessary balance. The subject battery feed circuit separates the two functions: a pair of poorly matched inexpensive power resistors provide the basic dc current; and associated pair of low power electronic circuits supply compensation signals to provide the necessary balance. The compensation signals are applied to the power resistors in a manner to obtain precision resistor (.+-.0.1%) characteristics from the inexpensive (.+-.5%) power resistors.

Dynamic impedance element for a battery feed circuit

This invention relates to line circuits and, in particular, to the apparatus contained therein for switching the ringing signal on to the communication pair which connects the line circuit to the telephone station set which it serves. Electromechanical relays provide an ideal switching function but require a significant amount of space while semiconductor switches do not require much space but provide an imperfect switching function which adversely affects the performance characteristics of the line circuit. The subject ringing apparatus makes use of a semiconductor switch to provide the ring relay function and incorporates additional circuitry to eliminate the difficulties associated with semiconductor switches.

Ringing application circuit

This circuit uses a simple structure of series-parallel connected capacitors and diodes to implement an n/m voltage divider circuit. There are n columns of series connected capacitors, which columns are all connected in parallel. The capacitor valves are selected so that in each column the ratio of charging capacitance to discharging capacitance is n:m. The diodes automatically switch the capacitor charging and discharging currents to the series-parallel connected capacitors.

Voltage divider circuit

Electronic battery feed circuits are connected across the communication pair, in parallel with the voice transformer, and serve as a dc path for loop current. These electronic battery feed circuits must provide both a low dc impedance to sink loop current and a high ac impedance so as not to shunt the ac signal away from the transformer. Prior art electronic battery feed circuits draw their bias current directly from the communication pair and this configuration tends to unbalance the line, provide too low an ac impedance, and provide too high a dc impedance. The subject electronic battery feed circuit obtains a low level bias current from the voice transformer and presents a low dc impedance to loop current. This particular circuit configuration eliminates hybrid balance problems and ac shunting of the voice transformer.

Battery feed circuit

The subject gyrator circuit is realized by a single amplifier and six resistors, which resistors are selected to satisfy a single equation. This permits great flexibility in setting the Z.sub.12 and Z.sub.21 impedance values without affecting the stability of the basic circuit.

Single amplifier variable gyrator

A sample and hold circuit is disclosed which employs a matched pair of operational amplifiers as a decoupling circuit to isolate the output of the sample and hold circuit from the sampling capacitor. Prior art decoupling circuits employ a simple isolation amplifier which has a tendency to charge the sampling capacitor with the isolation amplifier input bias and leakage currents. The disclosed decoupling circuit employs one of a pair of matched operational amplifiers as a self-compensating isolation amplifier which dynamically generates the bias and leakage currents found at its input while isolating the sample and hold output from the sampling capacitor. The other operational amplifier is connected in series between the isolation amplifier and the sample and hold output and functions to cancel the input bias current signal generated by the self-compensating isolation amplifier. Thus, the net quiescent current into the input of the decoupling circuit is essentially zero, thereby eliminating the capacitor charging problem of prior art isolation amplifiers.

Operational amplifier decoupling circuit

A sample and hold circuit is disclosed which employs a matched pair of operational amplifiers as a decoupling circuit to isolate the output of the sample and hold circuit from the sampling capacitor. Prior art decoupling circuits employ a simple isolation amplifier which has a tendency to charge the sampling capacitor with the isolation amplifier input bias and leakage currents. The disclosed decoupling circuit employs one of a pair of matched operational amplifiers as a compensation circuit to dynamically generate the bias and leakage currents found at the input of the other operational amplifier, which is employed as the sample and hold isolation amplifier. Thus, the net quiescent current into the input of the decoupling circuit is zero, thereby eliminating the capacitor charging problem of prior art isolation amplifiers.

Growing community of inventors

Westminster, CO, United States of America

Richard J Cubbison, Jr