V.32 / V.34 modem protocol

[ecco]

Hi, All
Please forgive me if this posting should be in another newsgroup.

I am reading about the ITU V.32 and V.34 recommendations. While I
have been able to find descriptions of the signal constellations and
coding schemes, I have had a tough time finding out information on the
communications protocol. Specifically, I want to know how the calling
and answering modem keep the dial-up connection alive when neither
party has any data to communicate.

If anyone has any info on this (or knows which forum would be a better
fit than .design), please let me know.

Thanks.

ecco

 

[JosephKK]

ecco [email protected] posted to sci.electronics.design:

Hi, All
Please forgive me if this posting should be in another newsgroup.

I am reading about the ITU V.32 and V.34 recommendations. While I
have been able to find descriptions of the signal constellations and
coding schemes, I have had a tough time finding out information on
the
communications protocol. Specifically, I want to know how the
calling and answering modem keep the dial-up connection alive when
neither party has any data to communicate.

If anyone has any info on this (or knows which forum would be a
better fit than .design), please let me know.

Thanks.

ecco

As best as i understand it, the telephone system treats it like any
telephone call (loop start, dialing sequence, connect, continue until
no loop[on-hook at either end]). If the there is no data to send the
modem may insert nulls or syns or there may be a bare carrier to
maintain synchronization and line adaptation. I figure that sending
nulls is most likely. It is also possible that a special idle symbol
is sent repetitively.