Basic Question on ISDN PRI trunk- Simutaneous incoming call capacity 1

[ForumUser01]

Hello Gurus,

very basic question on ISDN PRI trunk simultaneous call capacity- ex: If I have
2 PRIs from Carrier A : own DID range of 500 Numbers
2 PRIs from Carrier B : got its own DID range of 500 numbers

If all the trunks terminating on same phone system and users desks phones have 200 individual DIDs assigned assigned from Carrier A DID range... At any give time how many simultaneous 'incoming calls' we can have.

Iam thinking only 48 as Carrier B does not allow carrier A DIDs to pass via his trunks. For out going it should be OK- any trunk is fine.

If that is correct, and incase if we want to have 100/150 Simultaneous incoming calls, what normally the procedure? Need more ISDNs Bundled together or another kind of design..? Please suggest.

Thanks
MS

 

[wleong56]

Hope I understand your questions.
These are PRI and you mention 2 and I am assuming T1 (not E1)... I am not sure if these are FACILITY ASSOCIATED (FAS) or NON FACILITY ASSOCIATED (NFAS)
So potentially you can have... B a re the Barrier channel for voice and D is the signalling channel.
FAS=23B+1D and 23B+1D
NFAS=46B + 2D channels (one active D and one standby D)
or
NFAS=47B + 1D (one D serving both T1)

Simultaneus during peak, you can have 46 or 47 simultaneous incoming calls.

If you want to have a call capacity of 100/150 simultaneous calls... then you should design it for 150. For that you should buy an NFAS setup in this senario
NFAS=46B + 2D channels (one active D and one standby D)=2xT1
and 5xT1=120B channels.
This will be a little over 166 trunks.

In AT&T lingo, that would be a combination of package A, B and C.
Watch out for the limitation of an S8300 to support that many trunks. Anything S85xx and up should be OK.

Closing, it would be unsual to have that many trunks unless you are running some sort of survey and callers has 10 minutes or less to get queued to your trunks. Or this is a large and active call center, either with long or very short hold time. Anyway, I don't know.