[Asterisk-Users] T1 versus PRI

[pabelanger at codeslingers.ca]

Hello,

T1 CAS - Usually people with provision there lines for T1, for transfers (Blind
/ Hookflash transfer).  It is usually easier to setup.  The downside is all
information is passed inband.  ANI and DNIS is usually supported, but that it
it.  24 channels of voice.

T1 PRI - With ISDN, the major advantage is the amount of data you can access. 
There are 23B (voice) and 1D channel on every PRI.  Because information is
passed out-of-band, there are information elements available to extract the
data from (ANI, DNIS, CallerName, etc).  Transfer are a little more tricky,
TBCT or RLT are the formats, but the switch has to support this.  Also, when
doing a TBCT you will required a 2nd channel from the PRI for the setup back to
the switch (this only takes a few seconds, but it is 1 less channel no able to
answer incoming calls).

As for T1 CAS (robbed bit), I don't see a difference at all on answer compared
to PRI.

Usually, if you have to connect to an existing PBX, people will use a LineSide
T1 (T1 CAS (robbed bit) running the LoopStart protocol); atleast all the
installs I have done.

PB

Quoting gw at adcomcorp.com:

> Hello All,
> I was wondering.  What are the primary advantages to using a PRI over a
> T1?  As I understand it, the PRI terminates very fast, meaning you can
> do immediate answer and dial...  This is very handy on the BRI line I
> have on the asterisk.
>
> Can T1 signalling also do immediate answer, or does it just behave like
> a channelized pots line and ring as usual?
>
> I am trying to determine if I should use a pri between a pbx and
> asterisk, but PRI costs about double to implement.
>
> I do however enjoy the fast connect time...
>
> Thanks,
> Greg
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