Abstract: A passive optical network suitable for use as a telecommunications access network, having a head-end transmitting in a first optical frequency and one or more subscriber stations transmitting on a second common optical frequency. A carrier sense, multiple access protocol, with collision detection, is used, the collision detection being performed in the subscriber and head-end stations.

Abstract: 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.