Primary Rate Interface - wikipedia Primary Rate Interface This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. ( 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 bearer ( B ) channels and one data ( D ) channel for control purposes, for a total bandwidth of 24x64 - kbit / s or 1.544 Mbit / s. The E1 carrier provides 30 B - and two D - channels for a bandwidth of 2.048 Mbit / s. The first timeslot on the E1 is used for 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. Contents 1 ISDN service types 2 Application 3 See also 4 References ISDN service types The Integrated Services Digital Network ( ISDN ) prescribes two levels of service : Basic Rate Interface ( BRI ) : two 64 - kbit / s B channels and one 16 - kbit / s D channel, intended for small enterprises and residential service. Primary Rate Interface ( PRI ) for large organizations, with one 64 - kbit / s D channel and 23 ( 1.536 Mbit / s T1, a.k.a. `` 23B + D '' ) or 30, 64 - kbit / s B channels ( 2.048 Mbit / s E1, a.k.a. `` 30B + 2D '' ). Each B - channel carries data, voice, and other services. The D - channel carries control and signaling information. Larger connections are possible using PRI pairing. A dual T1 - PRI could have 24 + 23 = 47 B - channels and 1 D - channel ( often called `` 47B + D '' ), but more commonly has 46 B - channels and 2 D - channels thus providing a backup signaling channel. The concept applies to E1s as well and both can include more than 2 PRIs. When configuring multiple T1 's as ISDN - PRI 's, it 's possible to use NFAS ( non-facility associated signalling ) to enable one or two D - channels to support additional B - channels on separate T1 circuits. Application The Primary Rate Interface channels are typically used by medium to large enterprises with digital private branch exchange ( PBX ) telephone systems to provide digital access to the public switched telephone network ( PSTN ). The B - channels may be used flexibly and reassigned when necessary to meet special needs such as video conferences. PRI channels and direct inward dialing are also common as a means of delivering inbound calls to voice over IP gateways from the PSTN. See also Non-Facility Associated Signalling H channel Caller ID spoofing References Jump up ^ https://books.google.com/books?id=0LyDQgAACAAJ&dq=newton%27s+telecom+dictionary+16th+edition Jump up ^ https://www.itu.int/rec/T-REC-I.412-198811-I/en Jump up ^ `` A Technical Coverage of Primary Rate Interface ( PRI ) ''. ISPFast. Retrieved 18 June 2015. This article incorporates public domain material from the General Services Administration document `` Federal Standard 1037C ''. Retrieved from `` https://en.wikipedia.org/w/index.php?title=Primary_Rate_Interface&oldid=826012966 '' Categories : Integrated Services Digital Network Hidden categories : Articles needing additional references from January 2016 All articles needing additional references Wikipedia articles incorporating text from the Federal Standard 1037C Talk Contents About Wikipedia Deutsch Français Italiano Polski Русский Türkçe Українська Edit links This page was last edited on 16 February 2018, at 18 : 23. About Wikipedia

Question: isdn uses b & d channels. what is d channel use for
Answer: control and signaling information; data; carries control and signaling information; control and signaling information