| 摘要 |
In order to ensure continuous telephone service to a customer premises served by an ISDN line, without requiring that the customer maintain an additional POTS line as an emergency back-up to the normally used ISDN service, ISDN signalling circuits and network termination interface components are modified, so that, in the event of a loss of power to customer premises digital communications equipment, a communication link between an auxiliary POTS telephone and the normal ISDN communication path to the central office may be established. There need not be any modification of the central office switch, per se, so that the integrity of the ISDN communication path with the central office line card remains unaffected. As a result, the central office equipment can continue to conduct standard ISDN communications with the customer premises equipment, even though the customer is employing a POTS back-up analog phone.
|
