ASR-33 Data Format?

From: Eric Smith <eric_at_brouhaha.com>
Date: Thu Apr 1 12:59:02 1999

Hans wrote:
> AFAIK the US ISDN uses only 56K chanels - or am I wrong ?

No, both 56K and 64K ISDN B channels are available in most of the US.

But we were talking about using a 56K voice-band modem (V.90, X2, or K56flex)
on a POTS line. The server end uses ISDN.

The data rate on the POTS line is limited to 53 Kbps by FCC regulations.

The signalling on the POTS line is 8000 baud with up to 7 bits per symbol.

At the server end, the data is still 8000 samples per second, of 7 bits
each. However, those samples are presented digitally, so in some sense it
could be considered to be 56000 baud at the server end *only*. On the other
hand, to be decoded properly, the modulation technique is such that the
integrity of the byte framing of the samples must be maintained, so
effectively it really is still 8000 baud.

> > Anyhow, this is OT for another 7 years or so.
>
> Depends on personal experiance - I got my hands on ISDN
> equippment first in 1981, and used ISDN Parts for my own
> design first in 1985 (to rebuild an /370 Mainframe into

Yes, but the topic was 56K voice-band modems, which have not existed that
long.

Eric
Received on Thu Apr 01 1999 - 12:59:02 BST