Nortel Networks Corporation

Mark Bridger

Christopher Neville Tate

Roger J Williamson

Andrew David Wallace

Michael F Grant

Igor Kajetan Czajkowski

Jeffrey Farrington

Jonathan Beattie

A digital subscriber loop modem arrangement is arranged to respond to a fault condition so as to provide at least a voice lifeline service over DSL service on a digital subscriber line in which data and voice traffic are transported on a plurality of carriers. On detection of a power loss at the subscriber end of the line, the number of carriers is reduced so as to maintaining transmission only of those carriers transporting the voice traffic. This reduces the power demand which can now be met from the remote end of the line. A method of operating a digital subscriber loop modem arrangement under a fault condition so as to provide at least a voice over DSL service on a digital subscriber line in which data and voice traffic are transported on a plurality of carriers, the method comprising the steps of: replacing the data with random data, disabling those data carriers on which the random data is transported, and maintaining transmission of those carriers transporting the voice traffic.

Continuity of voice carried over DSL during power failure

Customer premises equipment for a telecommunications DSL subscriber is adapted to provide a lifeline voice service under a fault condition, e.g. a power failure at the subscriber station. The arrangement incorporates a number of switchable local subscriber ports each providing access to a respective telephone instrument, and a router circuit whereby, under normal conditions, voice calls may be routed each to a respective loop port. Under a fault condition the router directs an incoming call to a selected port to provide the lifeline service. Further calls may be barred when such a lifeline call is in progress.

Voice over digital subscriber line call redirection for lifeline service

A method, apparatus, and software for providing lifeline service during power failure affecting Customer Premises Equipment (CPE) in a Digital Subscriber Loop (DSL) arranged to carry voice traffic in band rather than on a separate analogue POTS band. The arrangement provides a reduced service, capable of supporting at least one voice call, to operate during such power failure and, where a single call is in progress during power failure, that call may be maintained during the transition from DSL to analogue POTS lifeline service. Where a call is in progress upon power restoration, the lifeline POTS service may be maintained until completion of the call so as not to interrupt a potential lifeline call.

Lifeline telephony provision for voice over digital subscriber line

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Hertford Heath, United Kingdom

Mark Bridger