Telephonic communications – Subscriber line or transmission line interface – Hybrid circuit
Patent
1989-12-15
1991-07-23
Dwyer, James L.
Telephonic communications
Subscriber line or transmission line interface
Hybrid circuit
379345, 379250, 379403, 379405, H04M 900
Patent
active
050349783
ABSTRACT:
The universal channel unit includes a channel interface circuit that uses a pair of fixed ratio transformers to terminate both two wire and four wire analog transmission facilities on a selectable basis. The universal channel unit also includes a plurality of signalling circuits, each of which is switchably connectable via the channel interface unit to provide a DC signalling interface to match the signalling format required by the associated analog transmission facility. The signalling circuits include: DX, FXO, FXS, and other DC signalling circuits. The AC component of the signals carried by the analog transmission facility is output to an adaptive impedance and balance circuit which functions to closely match the impedance of the analog transmission facility and minimize signal reflections under control of a microprocessor. This impedance and balance network is connected to a PCM interface that includes an adaptive echo canceller circuit as well as equalization and gain control circuits.
REFERENCES:
patent: 4598172 (1986-07-01), Eriksson
patent: 4771449 (1988-09-01), Kiko et al.
Bolinger Terry D.
Neely John A.
Nguyen Ninh T.
Dwyer James L.
Shehata M.
Xel Communications, Inc.
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