ISDN terminal equipment-resident mechanism for determining service profile identifiers and associated telecommunication switch protocol

An arrangement for enabling data terminal equipment to conduct digital communications via a central office switch over a telecommunications network to a destination site, including ISDN terminal equipment which is configured to interface said data terminal equipment over a local loop to said central office switch, said ISDN terminal equipment having a user interface through which directory number information is supplied by a user, and a communications controller, which is operative to control communications carried out by said ISDN terminal equipment, and which is programmed to format a service profile identifier required for conducting digital communications via said central office switch, in accordance with a service profile identifier detection routine which, when executed, performs the following steps:

• (a) attempting to register one or more SPIDs derived from one or more local directory numbers supplied through said user interface, and a selected one of a plurality of respectively different SPID formats;
• and
• (b) in response to successful registration of said one or more SPIDs in step (a),configuring said digital communications device for the placement of calls using the one or more SPIDs that has been successfully registered in step (a).