Editing Primary Rate Interface (section)

{{Short description|Telecommunication standard}}
{{More citations needed|date=January 2016}}

The '''Primary Rate Interface''' ('''PRI''') is a [[telecommunications]] interface standard used on an [[Integrated Services Digital Network]] (ISDN) for carrying multiple [[DS0]] voice and data transmissions between the network and a user.

PRI is the standard for providing telecommunication services to enterprises and offices. It is based on [[T-carrier]] (T1) transmission in the US, Canada, and Japan, while the [[E-carrier]] (E1) is common in Europe and Australia. The T1 line consists of 23 [[B channel|bearer (B) channels]] and one [[D channel|data (D) channel]] for control purposes,<ref>{{cite book|url=https://books.google.com/books?id=0LyDQgAACAAJ&q=newton's+telecom+dictionary+16th+edition|title=Newton's Telecom Dictionary: The Official Dictionary of Telecommunications & the Internet|first=Harry|last=Newton|date=15 January 2019|publisher=Telecom|isbn=978-1-57820-053-5 |via=Google Books}}</ref> for a total bandwidth of 24x64-kbit/s or 1.544&nbsp;Mbit/s. The E1 carrier provides 30 B- and one D-channel for a bandwidth of 2.048&nbsp;Mbit/s.<ref>{{cite web|url=https://www.itu.int/rec/T-REC-I.412-198811-I/en|title=I.412:ISDN user-network interfaces - Interface structures and access capabilities|website=www.itu.int}}</ref> The first timeslot on the E1 is used for [[Frame synchronization|synchronization]] purposes and is not considered to be a B- or D-channel. The D-channel typically uses timeslot 16 on an E1, while it is timeslot 24 for a T1. Fewer active bearer channels, sometimes called user channels, may be used in fractional T1 or E1 services.