In integrated services digital network (ISDN), a Network Layer identification for each terminal device associated an NT1, NT2, or B channel. The carrier assigns up to eight SPIDs per telephone number, which may be the 10-digit directory number (i.e., telephone number), perhaps with a prefix or suffix. See also B channel, ISDN, NT1, and NT2.
(Service Profile IDentifier) A number assigned to an ISDN line by the telephone company that indicates which services the ISDN device can access. The SPID is used by the central office switch, and depending on the type of switch, either one or two SPIDs or none at all are required per line. The SPID is usually the 10-digit ISDN telephone number with a couple of extra digits tacked on. For example, the SPID for the ISDN number (215) 489-2077 might become 21548920770101.