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

The inability of an ISDN equipment user to properly configure ISDN terminal equipment, even when provided with correctly assigned switch protocol, SPID and LDN parameters by a telephone service provider, is successfully remedied by a SPID/switch protocol detector. Upon being invoked by the user, the routine proceeds to conduct an iterative search of stored SPID formats associated with different central office switch protocols. SPIDs are assembled in accordance with the iteratively accessed SPID formats and directory number information that has been entered by the user. If an attempt to register a SPID is successful, the routine places a test call. If the test call is successful, the SPID and its associated switch protocol will have been identified, and the terminal equipment may place a call.