Inaudible noise on telephone lines...

["Andrew Kilgore" <amkilgore@xxxxxxxxxxxx>]

Hi all,

After much tinkering with two HV Phone/Serial add-on units, I've had to
face
up to the fact that I have sufficient noise on the phone line to prevent
both versions of the device from working properly. Version I unit could
detect on/off hook status correctly but had problems with detecting ringing
and DTMF tones. Version II unit (with the newest chip from CSI) has no
problems with DTMF or ring detection but is unable to detect on/off hook
status :o(

So, two questions:

1. Does anyone know of any type of filter I can try to eliminate the noise.
Having a cable modem I don't know too much about ADSL etc. but I do know
that it usuall requires a microfilter. Any similar devicethat I could
try...?

2. Failing this, is there any point in ringing my provider (NTL), informing
them of my problem and asking them to help...? (Long shot I know ;o)). What
would 'one' say to stand the best chance of getting something done...?

Below is a snippet from the csi website which describes the cause of the
problem

=======================================================
About 5% of users experience this problem. It is due to excessive noise on
your home's phone line. This isn't audible noise - it's 60Hz AC
"common
mode" noise. This means the noise appears on both phone line wires
equally,
and the noise is relative to earth ground. Because most phones only care
about the relative voltage between the two wires, they aren't affected by
this noise, and you won't normally even hear it. The problem usually occurs
when the phone lines run parallel to high-voltage AC power lines for
several
miles or more. This high voltage can induce noise onto the phone lines.
Unfortunately, there is nothing we are aware of that a homeowner can do to
eliminate this noise.
If the noise goes above 10 or 15 volts AC, the phone interface chip in the
version-2 phone devices may become unable to determine whether the phone is
on or off hook. This will also cause the phone device's green LED to show
the incorrect conditions. With the version-1 devices, the noise would have
a
different effect. Hook status would work fine, but touchtone (DTMF) and
caller ID detection could be degraded. We thought the newer version-2
devices would be immune to the noise, but they aren't (although they are
less susceptible than the version-1 devices that many users beta tested.

=======================================================

Many thanks,
Andy.


---
Outgoing mail is certified Virus Free.
Checked by AVG anti-virus system (http://www.grisoft.com).
Version: 6.0.620 / Virus Database: 399 - Release Date: 11/03/2004



UK Home Automation Meet 2004 - BOOK NOW!
http://www.ukha2004.com

http://www.automatedhome.co.uk
Post message: ukha_d@xxxxxxx
Subscribe:  ukha_d-subscribe@xxxxxxx
Unsubscribe:  ukha_d-unsubscribe@xxxxxxx
List owner:  ukha_d-owner@xxxxxxx