[ale] PBX

[Curt Smith]

On Wed, 11 Dec 1996 tomk%westgac3 at dragon.com wrote:

> >     several 28.8 and 33.6 modems that we use for Notes & NT.  Connections 
> >     speeds top off around 24.0 (24,000Kbps).  I've seen 26.4 a few times 
> >     but not many.  We think we have narrowed the problem down to our PBX 
> >     system.  I think the PBX systems is consistently degrading the line to 

33.6 is a methical connect rate achievable in laboratory like conditions
or if you're only a mile from your digital CO.  Which I'm sure a bunch of
you will quickly say that they get 28.8 or 33.6 connects all the time.
I'm happy somebody does.  

Fact is, a large portion of us can't because our CO is junk, or we are served
by a CO 10 miles away and there's 10 wire nutz between our house and the
CO...

Feel lucky that your PBX only inserts a very small amount of distortion,
jitter and echo that you get a high speed connect as you claim.
Our PBX limits at 9600, believe-it-or-not.

Another issue for >>26kb modem connects exists in your house.  Occationaly
there will be chatter in the .modem group, but it's obviouse when told;
All those periferals you have hanging off your phone line at home, fax,
3 extension phones etc etc all serve to nutz the impedance and increase
echos back to the CO side.  This affects the error rate at very high
modem speeds.  Either get a seperate phone line at home, or experiment
by taking all those periperals off the circuit.  Some times this isn't
even good enough, because the echos generated by the spider web of
extension runs off the phone line and wire taps with some resistance
cause the echos as badly as the peripheral itself.  A straight run of
good phone wire from the jack on the outside of the house is best for
modem use.

Good luck.


Curt Smith
curts at compgen.com