System interfaces
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System functions and features as of R3.0
syd-0367/1.3 – R3.0 – 03.2013
2. 1. 2 Primary rate interface PRI
A primary rate access is a digital network interface for connection to the public net-
work or the private leased-line network. It can be set for the protocols DSS1 (public
ISDN network) and QSIG / PSS1 (private leased-line network).
A primary rate access has thirty 64 kbit/s user information channels and one 64
kbit/s control and signalling channel (30B+D). One call or data connection can be
set up on each bearer channel (B channel) simultaneously and independently of
the other B channel.
CAS (channel-associated signalling) is also used in some countries (e.g. Brazil). With
this method the signalling data is transmitted over the voice channel. The type of
signalling can be selected for each PRI interface in CM_2.1.2.
Note:
Primary rate accesses can only be used as point-to-point connections.
NT1: Network Terminal
U2/U/T2/T:ISDN reference points
30B+D: Primary rate access channels
2B+D: Basic access channels
DSI: Digital terminal interface DSI
BRI-S: ISDN terminal interface
FXS: Analogue terminal interface FXS
Fig. 7 System with basic and primary rate accesses
Fig. 8 Primary rate access in a private leased-line network: PINX-PINX connection
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