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).
