In the integrated service digital network (ISDN), a 64-kbps channel that bears the end user data, or payload. Standard ISDN interfaces include multiple B channels and a D channel (Delta channel or Data channel) for signaling and control purposes. Basic rate interface (BRI) comprises two B channels and one D channel, and is often referred to as 2B+D. Primary rate interface (PRI) comprises 23 B channels, plus a D channel, is compatible with North American T1 and Japanese J-1 standards, and is often referred to as 23B+D. Primary rate access (PRA) comprises 30 B channels, plus a D channel, is compatible with European E-1 standards, and is often referred to as 30B+D. (Note: A 32nd channel is added for overhead and alarms.) See also BRI, D channel, E-1, ISDN, J-1, payload, PRA, PRI, and T1.