Primary Rate Interface

(PRI) A type of ISDN connection. In North America and

Japan, this consists of 24 channels, usually divided into 23 B

channels and 1 D channel, and runs over the same physical

interface as T1. Elsewhere the PRI has 31 user channels,

usually divided into 30 B channels and 1 D channel and is

based on the E1 interface.

PRI is typically used for connections such as one between a

PBX (private branch exchange, a telephone exchange operated by

the customer of a telephone company) and a CO (central office,

of the telephone company) or IXC (inter exchange carrier, a

long distance telephone company).

(1995-01-18)