Missing or incorrect SPIDs

In most North American ISDN implementations, Service Profile Identifiers (SPIDs) must be configured into terminal equipment; that is, computers, telephones, or other ISDN-enabled devices, not their network termination devices (NT-1 or NT-2). Without a SPID, the ISDN terminal device cannot perform layer 3 initialization and hence cannot make calls, even though layer 2 initialization successfully completes. If you are unsure about your SPID setting, contact your ISDN service provider.