Tie/communications, Inc.

Ira Guzik

Alan Bloch

Frank A Coviello

Candido Puebla

Each of the station sets in the system generates a continuous, current-modulated digital data stream carrying information concerning the status of pushbutton-actuated switches associated with a particular service or feature. This data stream is transmitted via a phantom pair over standard four-wire cable to an associated station card in the key service unit, which receives and decodes the data, implements any service requested at the associated station set by closure of a pushbutton-actuated switch in the station set, and generates a continuous voltage-modulated digital data stream carrying instructions for the connection of the station set speakerphone to either the first or second talk path formed by the first and second conductor pairs in the standard four-wire cable, for energization of light-emitting diodes associated with the pushbutton-actuated switches in the station set, and for controlling background music transmission to the associated station set. This data stream is transmitted via the aforementioned phantom pair to the station set, which receives and decodes the data and carries out the instructions contained therein. Each station card and each station set incorporates a stored-program digital microcomputer for decoding the received data and for generating the data to be transmitted. Each station card also includes a series of crosspoints in the form of field-effect transistors, the gate electrodes of which are connected to crosspoint latches controlled by the microcomputer. Each crosspoint has an associated input terminal in a status multiplexer which receives data from the passive port to which the associated crosspoint is connected. Each crosspoint and its associated status multiplexer input terminal constitute an active port. Each station card also includes at least one passive port for hotline connection to an active port of another station card or cards, and may also include a passive port for connection to the active ports of one or more link cards. Other system component circuits are disposed on line cards having a single passive port, an internal conference card having a single passive port, a page card having multiple passive ports, a register card or cards connected to the link card or cards, and a tone generator card.

Electronic key telephone systems

The disclosure relates to a four conductor circuit arrangement providing two communication channels between a control unit and a terminal device. Power feed and bi-directional signalling are accomplished simultaneously over the same four conductors used for the two commmunication channels without interference. The signalling from the control unit to the terminal is accomplished by means of a voltage modulator circuit in the control unit by which voltage pulses are transmitted via a phantom circuit arrangement over the four conductors to the terminal unit. The voltage pulses are sensed from the phantom circuit in a data receiver which is located at the terminal unit. Connected to the phantom circuit in the terminal unit is a voltage regulator circuit which receives power from the control unit via the four conductor phantom circuit interconnecting the control unit and the terminal. In series with the voltage regulator circuit is a constant current sink and an inductor. A current modulator circuit is provided in parallel for impressing current data pulses generated in the terminal onto the phantom circuit, which are, in turn, received by a receiver circuit in the control unit. A preferred data format is disclosed as a method for transmitting information between the control unit and the terminal. The preferred embodiment for the disclosed four conductor communication circuit and the disclosed data format is in a key telephone system in which the control unit is a station card in a key service unit and the terminal is a key telephone station set.

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Fairfield, CT, United States of America

Ira Guzik