Gte Automatic Electric Laboratories Incorporated

David Q Lee

Richard M Rovnyak, Sr

Donald W McLaughlin

Julius Jusinskas, Jr

Dinesh K Srivastava

John A Calder

Richard Michael Rovnyak

A line voltage sensor and dial pulse repeater circuit for use in conjunction with a digital PABX telephone system connecting a subscriber station to a switching center providing for detection of off-hook condition of the subscriber's set, detection of irregularly shaped dial pulse and correction of the irregularly shaped dial pulses to allow accurate reconstruction of the dial pulses originally transmitted via the subscriber's set.

Dial pulse sensor and repeater circuit

A call for service and continuity sensor circuit for use in conjunction with a trunk circuit of a digital PABX telephone system interfacing with a central office via ground start signalling providing for detection of a call for service signal to the PABX by the central office. This circuit also provides the means to effect an open circuit for both signalling and transmission conditions in order to prevent excess loading of the trunk circuit during these conditions. This circuit provides a precise and stable threshold detection level necessary for accurate sensing of the trunk circuit conditions mentioned above despite parasitic leakage current, induced longitudinal power line voltages, and earth potentials sometimes existing on the line connecting the PABX to the central office.

Call for service and continuity sensor circuit

An AC supervisory signal detector circuit for use in conjunction with a trunk circuit of a digital PABX telephone system interfacing with a central office providing for detection of relatively low frequency AC voltages which may be superimposed upon a DC bias voltage of either polarity. The circuit is equally responsive to various frequencies used in supervisory type signaling.

AC supervisory signal detector circuit

A detector circuit for use in conjunction with a trunk circuit of a PABX telephone system interfacing with a central office providing for constant monitoring of normal or reverse battery application by the central office during the high impedance idle state or the low impedance busy state. In addition, the circuit provides for detection of: proper loop closure, electrically shorted tip and ring leads, open circuit condition of tip and ring leads or a grounded ring lead. Furthermore, the circuit indicates when current flow of proper magnitude is sensed during normal or reverse battery conditions.

Detector circuit for sensing battery polarity and loop closure

A circuit for electrically preconditioning a telephone line and switching an associated ringing generator on and off at the instant of opportune circuit conditions to eliminate circuit transients. The line circuit is switched by means of a relay so that an equipotential charge exists on either side of the switching contacts at closure and with zero current through the contacts at opening to eliminate suppression devices.

Line conditioning and transfer circuit

A method of providing a multi-port conference circuit for use in a telephone switching system employing pulse coded modulated signals for transmission and supervision. Samplings of coded information are employed as a source of conference data and comparison with the digital information contained therein is employed to choose the speaker in a conference group. Included circuitry provides compensation for degradation caused by speech clipping and noise.

Conference circuit for pulse coded modulated telephony

A method of providing a multi-port conference circuit for use in a telephone switching system employing pulse coded modulated signals for transmission and supervision. Samplings of coded information are employed as a source of conference data and comparison with the digital information contained therein is employed to choose the speaker in a conference group.

A regimented memory arrangement in which 'Read' and 'Write' operations take place simultaneously. Three-way communications are facilitated by the technique disclosed.

Memory operation for 3-way communications

A precise tone injection circuit for injecting tone signals to a constant current junctor circuit in a two-wire balanced circuit. The tone injection circuit includes a pair of transistors operating as constant current sources feeding the respective ones of the two wires. A phase splitter amplifier couples a tone signal to the base electrodes of the transistors to change the current through their collector electrodes via the emitter circuits thereof at a rate and frequency of the tone signals at the base. Since a two-wire balanced circuit is used, and the injected signal currents to each wire are 180.degree. out-of-phase, in-phase signals, that is, noise and voltage fluctuations, are reduced or rejected.

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Chicago, IL, United States of America

David Q Lee