Avaya 03-300430 User Manual

ISDN-PRI D-channel signaling can be combined with a group of B channels in three basic ways:

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FAS (facility-associated signaling)

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NFAS (non-facility-associated signaling)

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Backup NFAS signaling

In a FAS signaling group, the 24

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 port of the TN464 UDS1 Interface circuit pack or MM710 DS1 

Interface Media Module carries D-channel signaling for up to 23 B-channel ports on the same 
circuit pack or media module.
In an NFAS signaling group, the 24

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 port of one TN464C or higher suffix UDS1 Interface or 

MM710 DS1 Interface Media Module can carry D-channel signaling for B channels on several 
other DS1 circuit packs or DS1 Media Modules, as well, including TN767s and TN464Bs. The 
24

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 port on the other circuit packs or media modules can be used as a B channel. A D channel 

in an NFAS group can signal for B channels on a total of 20 DS1 circuit packs or media 
modules.
D-channel backup provides increased reliability, which is highly desirable since NFAS permits a 
D channel to signal for many more B channels. NFAS allows the administration of a backup D 
channel that remains in a standby state until the active D channel goes down. If so, the backup 
D Channel takes over and provides signaling for every B channel in the signaling group.
The operation of the entire ISDN-PRI signaling group depends on several other entities: 

●

 / 

 / 

: The ISDN-PRI signaling channel ports, the TN464 UDS1 

Interface circuit pack or MM710 DS1 Interface Media Module, on which the D channels 
reside, and the system link that is carried over the packet bus to the processor. 

When there are problems with the ISDN-PRI signaling group, also investigate 

on page 2175, and 

on page 1799, as appropriate.

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