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US 4,727,578 AGranted
Telephone system
AssigneeTrillium Telephone Systems Inc.
InventorGerald Molnar
Life of this patent
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AssigneeTrillium Telephone Systems Inc.
InventorGerald Molnar
Estimating the term…
A key telephone system comprised of a key service unit connected to a plurality of local sets via four-wire conductors for providing full duplex signal communication between the key service unit and sets. Signals are carried by a first pair of each of the conductors for unidirectional transmission of signals from each set to the key service unit, and the remaining pair of conductors carries signals transmitted by the key service unit for reception by one or more of the sets. Four-to-two wire signal conversion and line impedance balancing is effected by one or more trunk circuits of the key service unit in the event one or more of the local sets are connected via the key service unit for communication between the sets and the outside telephone lines. As a result of separate unidirectional communication paths being provided between individual ones of the subscriber sets and the key service unit, via the four-wire conductors, the impedance balancing function of the trunk circuits is independent of the length and quality of the four-wire conductors. Each of the trunk circuits preferably incorporates an electronic telephone circuit for performing the four-to-two wire signal conversion as well as AC and DC termination and loop length gain equalization for signals carried by the outside telephone lines. The key service unit and subscriber sets of the telephone system are inexpensive, compact and highly efficient as a result of minimizing the number of four-to-two wire conversions therein.
A telephone system for connection to one or more outside telephone lines having predetermined line impedances, comprising:
In a telephone system including voice switching means for connection to one or more subscriber sets via a plurality of local four-wire telephone conductors, and to one or more outside telephone lines having predetermined line impedances, a plurality of trunk circuits connected to respective ones of said outside telephone lines and said four-wire telephone conductors, each trunk circuit being comprised of an electronic telephone circuit for connection to corresponding ones of said telephone lines and said four-wire telephone conductors, including means for matching said predetermined line impedances, providing DC termination of said telephone lines, generating side tone in the event a communication path is established between one or more of said sets and said corresponding telephone line, performing loop length gain equalization of signals carried by said outside telephone lines.
Dependencies are inferred from the claim text.