Short for
Primary-Rate Interface, a type of
ISDN service designed for larger organizations. PRI includes 23
B-channels (30 in Europe) and one D-Channel. In contrast,
BRI (Basic-Rate Interface), which is designed for individuals and small businesses, contains just two B-channels and one D-channel.
PRI service is generally transmitted through a T-1 line (or an E1 line in Europe).