Primary rate interface
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The primary rate interface (PRI) is a telecommunications standard for carrying multiple DS0 voice and data transmissions between two physical locations.
All data and voice channels are (ISDN) and operate at 64 kbit/s.
North America and Japan use a T1 of 23 B channels and one D channel. Europe, Australia and most of the rest of the world use a slightly higher capacity E1 of 30 B channels and one D channel.
Fewer active B channels (also called user channels) can be used for a fractional T1. More channels can be used with more T1's, or with a fractional or full T3 or E3.
See T-carrier for DS0, T1, E1, T3, E3 and other carrier communications terms.
Sources: From Federal Standard 1037C
External links
* Asterisk Telephony wiki PRI [1] (http://www.voip-info.org/wiki-PRI)