(PMOD) Another reason people might not get 56K connections even if the server is ISDN PRI. :-(
James Courtier-Dutton (jcdutton@lucent.com)
Tue, 1 Jun 1999 23:38:59 +0100
Hello
I was wondering what experience and tests people have done comparing modem
connections against ISDN BEARER CAPABILITY and modem connect speed. Where
are 2 most common BEARER CAPABILITIES which can carry a voice call to the
ISDN PRI lines.
1) Speech
2) 3.1Khz Audio.
According to the ISDN specifications,
(2) is the only type which should be used with modems if you wish to get 56k
connects. It specifies that the connection should pass a certain amount of
bandwidth and it suggests modem or fax use. (There is specific G3 fax BEARER
you can use for fax).
(1) Speech, is just a best effort basis, and is open to extra voice
compression etc, not necessarily requiring extra A->D conversions.
Unless you get your analogue line set to 3.1Khz Audio, each call may vary in
voice quality depending on congestion etc. With 3.1Khz Audio, quality should
be consistent.
This is not necessary stating facts or recommendations, it is just asking
for any real world tests, if anyone has done them. Some telcos might not
even comply with the ISDN Specifications as much as they should. I suspect
most calls will be presented as (1) in problem areas, and most people with
few problems will see (2). All this is just theory, whats out there in the
real world is what I am interested in.
Cheers
James
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