Wescom Switching, Inc.

Rockwell International Corporation

Wescom, Inc.

John F Regan

Satyan G Pitroda

Byung C Min

Robert F Wojcinski

Richard S Surma

Ronald C Fischer

Bakulesh A Mehta

A switching regulator with controlled simulated load has a control which connects and disconnects the simulated load to the output of the regulator. The control is responsive to an error signal of a first comparator. A second comparator receives the output of said first comparator and produces a control signal for the simulated load when the regulator output reaches a predetermined level.

Switching regulator with controlled simulated load

An improved electronic hybrid for coupling signals between two wire and four wire transmission circuits. The hybrid includes a pair of amplifiers associated with a pair of terminating impedances which are serially connected between the amplifier outputs and the two wire port. The amplifiers driving the two wire port through the terminating impedances are biased to couple a dc potential to the two wire line whereby the terminating impedances serve as battery feed resistors. Each amplifier-impedance arrangement includes a feedback circuit connected from the junction between the impedance and the two wire port and an input of the amplifier for providing positive feedback for the amplifier so that the output impedance of the hybrid is maintained at a desired level using battery feed resistors of smaller value than heretofore required. The result is the ability to drive longer loops through the smaller series impedances while at the same time exhibiting the desired terminating impedance.

Electronic hybrid

In a system of parallel switching regulators sharing a common load, each regulator generates controllable pulses from an unregulated d-c. voltage source and then smoothing those pulses to form a d-c. output that varies according to changes in the pulses. A comparator controls the pulses according to the differential between a reference signal and a feedback signal, and an output resistor is connected between the comparator and the load. A reference signal source generates a reference signal for the comparator in a first one of the regulators, and the load side of the output resistor in the first regulator is connected to the feedback signal input to the comparator in that regulator so that the load voltage is determined by the reference signal for the first regulator. The comparator side of the output resistor in the first regulator is connected to the reference signal input to the comparator in a second one of the regulators, and the comparator side of the output resistor in the second regulator is connected to the feedback signal input to the comparator in the second regulator so that the current supplied to the load by the second regulator is equal to the current supplied by the first regulator.

Switching d-c. regulator and load-sharing system for multiple regulators

A digital conferencing arrangement for use in a digital telecommunications switching system. Digital coded signals representative of sampled analog signals are compared and the results of the comparison noted to identify the present speaker in the conference. A comparison result indicating a proposed new speaker initiates a delay interval during which subsequent samples are compared to assure that the proposed new speaker indeed has the largest analog signal during the delay window. Upon verification of the proposed new speaker, the control of the conference circuit is transferred to him.

Method and means for digital conferencing

An apparatus and method for testing for faults in an analog-to-digital (A/D) section and a digital-to-analog (D/A) section of a code converter in a digital time division, multiplex telecommunications system are disclosed. The A/D section is tested by connecting a digital test pattern via the switching network to the D/A section and monitoring for faults by comparing the resulting output to a reference value. The A/D section is tested by interconnecting the A/D section to be tested between a first previously tested D/A section and a second previously tested D/A section and then connecting the digital test pattern to the first D/A section while monitoring the output of the second D/A section for faults.

Method and apparatus for testing analog-to-digital and digital-to-analog

A voice-frequency RC-active filter comprising a plurality of resistors and generalized impedance converter networks for synthesizing the frequency response of a preselected LC filter. Each generalized impedance converter network includes a pair of operational amplifiers and a plurality of impedances Z1, Z2, Z3, Z4 and Z5 interconnected with the amplifiers to provide the network with a driving point impedance ##EQU1## in which at least one of the impedances in both the numerator and the denominator of Zi includes a film-type resistor. At least one of the film-type resistors included in the impedances Z1, Z2, Z3, Z4 and Z5 is functionally trimmed to tune the filter. The capacitors in the filter are preferably discrete polycarbonate capacitors with a capacitance tolerance of .+-.5%, and all having the same value.

Voice frequency RC active filter

A telephone system usable for example in hotels or the like and in which each of a plurality of telephone sets is equipped with a special status indicator or signal light as well as the usual bell, the system being characterized in that the indicator is automatically excited without ringing the bell by voltages applied from the ring generator whose output signal is connected across the tip and ring leads of a telephone line when the latter is placed in a special status (message waiting) by a status signal in the control unit. The ring generator is constructed to produce special status indicator excitation voltages during the 'bell silent' intervals of its output signal, and the indicator is periodically actuated by connecting that output signal across the tip and ring leads of telephone sets, which are in the special status, during at least a portion of such intervals.

Methods and apparatus for special status indication in telephone systems

An electronic hybrid for coupling signals between two wire and four wire transmission circuits, and capable of meeting the operating requirements of practical telephone systems. The hybrid includes a pair of terminating impedances serially connected between the two wire port and the circuitry driving that port, the impedances being precisely matched and coupled to a.c. ground, thereby providing a hybrid with excellent longitudinal balance. Amplifiers driving the two wire port through the terminating impedance may be biased to couple a d.c. potential to the two wire line whereby the terminating impedances serve as battery feed resistors. Reverse signal recovery is provided by an amplifier differentially connected to the two wire port, achieving excellent longitudinal rejection and further allowing the amplifier to serve a supervisory function. Two of such hybrids, connected back to back, with amplification interposed therebetween, form an improved transformerless repeater. In this embodiment, the amplifier may be constructed to be of variable gain, with the gain automatically adjusted as a function of sensed loop current, whereby the repeater may be installed without manually adjusting the amplification to suit the loop length.

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Lombard, IL, United States of America

John F Regan