Difference between ISDN Data Call & ISDN Voice Call

[Akki]

Dear All,

I'm in the process of understanding the ISDN PRI, studying the
Q.931, Q.921 also googling around to get deep into the basics,
but came across one basic doubt relating to the data call and voice
call.

As of my understanding the ISDN PRI differentiates between voice call
and data call to some extent, but the call control info in the
D-Channel
is almost similiar to both type of calls (correct me if I'm wrong
here).

So I was just digging deep into the internals of Call Control details
relating to the data call and voice cal, like difference between Data
Call
and Voice Call,
I tried googling through, but not got the exact info what I'm looking
into,
So please do help me in understanding the ISDN PRI voice call and data
call.

any pointers in this regard will be help ful !!

many thanx in advance,

--Ganesh

[Stefan Emilius]

Dear Ganesh,

as far as I know, there is no difference in the data structure of voice
and data calls. The cause to differentiate between is to make it
possible to use different type of endpoints with the same calling
number. So you can use i. e. a telephone, a G4 fax and an ISDN router on
the same BRI bus with the same ISDN number but only the router takes the
call if a data call comes in. Or only the phone rings if there is a
voice call.
On a PRI you can configure the PBX to separate incoming calls to
different BRI on FXS ports on the PBX, depending the type of the calls.

Hope this helps.

Greetings from munich
Stefan

Sometimes the world is easier as it looks on the first view.
Unfortunately only sometimes.

Akki schrieb:

[Phil McKerracher]

"Akki" <gkum...@buffalo.com> wrote in message
news:1165216961.7...@16g2000cwy.googlegroups.com...

> So please do help me in understanding the ISDN PRI voice call and data
> call.
>
> any pointers in this regard will be help ful !!

Voice and data calls are both usually passed through the network
transparently. The main reason for signalling them differently is to give
the terminal at the answering end a chance to refuse the call if it doesn't
like the type. For example, a telephone would refuse a data call, and a
computer would refuse a voice call.

The network will often intervene with voice calls if they are international
though, to convert A-law to mu-law, or to apply echo cancellers or echo
suppressors.

Also, there are still some trunks in the US that can only handle 7-bit data,
which is fine for voice but not for data calls, so knowing the type helps
the network to route them correctly.

You might find my ISDN tutorial at www.mckerracher.net/isdn helpful.

--
Phil McKerracher
www.mckerracher.net

[Akki]

Dear Stefan & Phil,

Many thanks for the detailed explanation, thanks a lot.
So there is no much of a difference between the ISDN voice Call and
Data Call,
other than the remote side identification whether to accept/reject the
call.

I'm looking at the Q.931 and Q.921 to understand in depth of the ISDN
Call Control and layer 2 handshaking, the tutorial helped me a lot.
The ISDN tutorial is very informative, got a good(short n sweet, to the
point) understanding of the Layer 1,2 & 3 of ISDN.

Thanks again.

--Ganesh