Bell Telephone Laboratories

Robert M Smith

Charles R Baugh

Dennis Bryan James

Chao Kai Liu

James R McEowen

Tse L Wang

There is disclosed an office communication system adapted to handle both bursty and continuous data transmission over a single transmission facility to a central switching network. A programmable station controller is used at each station location to interface a number of transmission inputs to the single communication link. The programmable station controller is arranged to statistically multiplex the inputs associated with the bursty data while allowing the continuous data to pass on dedicate time slots. Transmission compatibility between the types of data transmission received from the bursty and continuous data inputs is assured by subdividing the transmission on the single link into frames having four time slots. A fixed number of time slots of each frame are assigned by a central controller to active ones of the continuous data inputs while other time slots of each frame are assigned to the multiplexed bursty data inputs. One of the time slots of each frame is utilized for communicating control information between the programmable station controller and the central switching network controller.

Communication line interface for controlling data information having

There is disclosed a digital loop for interconnecting a number of data interchangers, each data interchanger connectable over a single high speed communication link to a remote station controller. The high speed link is arranged to bidirectionally transfer both bursty and continuous data to and from the data interchanger. A central controller is serially inserted in the digital loop and serves to assign time slots in a frame for information exchange between the various programmable data interchangers. Each frame contains a first field for data interchange between the data interchangers and the central controller; a second field having time slots assignable under control of the controller to a specific set of data interchangers for transferring information from the continuous data inputs; and a third field having time slots assignable under control of each data interchanger for transferring information from the bursty data input. The controller in cooperation with the data interchangers varies the size of the fields of each frame such that the portion of the field associated with continuous communication expands and contracts as traffic flow changes thereby increasing or decreasing the number of time slots available for the transfer of bursty data.

Digital loop switch for controlling data information having differing

A small program controlled communication system is disclosed having user changeable feature and line selection control. Associated with each station is a set of switches which are used to associate the various central office lines with the available nonlocking station pickup keys. The user, by setting the switches, can establish any line as a prime line and may select which other lines appear at the station. The setting of the switches also controls various other features available to the station, such as common audible, and privacy. The system is arranged such that the processor interrogates the switches periodically and translates the setting of the switches, which are human factors coded, into machine control codes which are stored in the main memory.

Program controlled communication system having individually

In order to reduce the signal loss in a telephone line switching and conferencing system there is interposed between each line and the switching matrix a monobus port circuit arranged to convert a transmitted telephone signal into an equivalent current source. The currents from several monobus circuits are added in a bus resistor before distribution back to the individual monobus circuit where the original signal is subtracted from the bus signal. The resultant signal is transmitted to the telephone receiver. When the switching matrix crosspoint resistance is negligible, the component of the bus voltage measured at the current source output which results from current generated from each line is equal and opposite in magnitude to the voltage generated in the line. In any given line these voltages cancel each other, thereby eliminating the feedback signal. In situations where it is desired to use crosspoints having an unknown resistance, the voltage returned from the monobus does not exactly match the locally generated voltage because of the voltage drop across the crosspoint and thus a feedback signal of unknown magnitude is applied to the telephone line. This unknown deviation of signal gives rise to gain contrast from one connection to the next and modifies the return loss in an unpredictable fashion. This problem has been solved by separating the connections of the monobus into transmit and receive paths and connecting each path to the bus through a separate crosspoint.

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Holmdel, NJ, United States of America

Robert M Smith