BG> How long is a piece of string... ?



Twice the distance from the middle to one end!

Which came first, the chicken or the egg? The rooster!

I've been sitting back, watching the on-going saga of "The Modem-Ones" and

can't help but laugh 'cos even tho I've only got a 14.4k ,EC-less modem,

I've never had any problems with TMTL that could be attributed to the modem.

The general idea seems to have swung around to it being a Telescum/line level

problem. I tend to agree with this. I was a Tech-In-training with the P.M.G.

when I left school and one of the first things you learn is the

characteristics of your average telephone line. They were designed and built

for voice operation (modems weren't even thunk ov then) with a bandwidth of

from 300cps to 3000cps and a nominal impedance of 600 ohms. The loop 

resistance can be as high as 6000 ohms.These figures were quoted from 

subscriber to exchange. Telescum used to quote a maximum of -9dBm permitted

line out-put to stop (read "reduce") cross-talk between ajacent
pairs of wire

in cables. I suspect that most of the subscriber lead-in and street cables

are still the original as-laid stuff which consists of single-strand, 

hard-drawn copper with on-average 11 wrapped-only joins between each subscriber

and the exchange. If you want reliable data exchange, you have to ask Telescum

for a "data grade line". If you complain about modeming on a normal phone

line, Telescum will send a token technician out who will put a very 

complicated looking meter across your lead-in block, try to look wise and

then tell you that the problem MUST be in your modem 'cos your line is 

"balanced". "Balanced" just means that he reads approx.
the same impedance

from both legs to earth (that is, provided you actually have TWO wires 

connecting you to the exchange. A lot of buildings that had another phone

installed after the first one sometimes had the original pair split and

both phones used a single line with earth return.)

It's a bloody wonder that  modems work at all when you start using micro-wave

and optical links. Each channel in a link is frequency shifted at least twice

and is not the same signal at the end as what started. Makes it a bit hard

to get a reliable link for you foreigners #:^}

Regards, Robert.





...     Time flies like an arrow.  Fruit flies like a banana.



--- PPoint 1.92