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ISDN Interfaces

ISDN provides two basic types of service, Basic Rate Interface (BRI) and Primary Rate Interface (PRI). J-series devices support both ISDN BRI and ISDN PRI.

ISDN BRI is designed for high-bandwidth data transmissions through existing telephone lines. The copper wires that make up much of the existing telephony infrastructure can support approximately 160 Kbps, which provides enough bandwidth for two B-channels and a D-channel, leaving 16 Kbps for any data framing, maintenance, and link control overhead.

ISDN PRI is designed for users with greater capacity requirements than can be met with ISDN BRI. In the United States, the most common PRI supports 23 B-channels and 1 D-channel, totalling 1,536 Kbps, which is roughly equivalent to a T1 link. In Europe, the most common PRI supports 30 B-channels and 1 D-channel, totalling 1,984 Kbps, which is roughly equivalent to an E1 link.

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