Telephonic communications – Subscriber line or transmission line interface
Patent
1993-11-29
1995-08-15
Dwyer, James L.
Telephonic communications
Subscriber line or transmission line interface
379 5, 379 6, 379413, 370 13, 370 14, 370 15, H04B 346
Patent
active
054426979
ABSTRACT:
The need to equip a digital data service termination with the ability to decode digital loopback commands is obviated by a relatively simple hardware modification of a four wire telephone circuit connecting an office channel unit and customer premises equipment. In addition, the signal processing and test control firmware of the office channel unit equipment (OCU DP) is modified so as to realize a simplified circuit configuration for performing loopback testing of the four wire circuit. The hardware modification of the four wire circuit connecting the office channel unit and the customer premises involves the use of a sealing current-dependent relay circuit that responds to respectively different sealing current flow states: normally; interrupted; and reversed, as converted by the OCU DP. The present invention is particularly useful in subscriber loop circuits that are less than 10,000 feet in length, whereby the need for additional amplifier and noise reduction components is obviated.
REFERENCES:
patent: 4766594 (1988-08-01), Ogawa et al.
patent: 4984250 (1991-01-01), Koyama
patent: 4984262 (1991-01-01), Kumozaki et al.
patent: 5224149 (1993-06-01), Garcia
Harris Norman R.
McGary John S.
Adtran Corporation
Dwyer James L.
Saint-Surin Jacques M.
Wands Charles E.
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