Off-topic informational anti-spam anecdotal

From: Philip.Belben_at_powertech.co.uk <(Philip.Belben_at_powertech.co.uk)>
Date: Wed Jul 22 13:10:43 1998

Tony ended his long discourse on telephones with:

> In practice, you're not going to damage the exchange no matter what you do
> to the line at the subscriber end. The incoming lines are protected by an
> array of spark gaps (probably gas filled), fuses and 'heat coils'. The old
> electromechanical exchanges were certainly protected against lightening,
> contact between telephone lines and (600V-ish) power lines, etc. Mains, at
> the far end of the line, is trivial in comparison.

ISTR that at our sites (electricity supply industry) we have to install
special isolators on phone lines if the rise in local earth potential
due to an earth fault exceeds 650V. Such sites are known as "hot
sites". The implication is, anything less than 650V to ground the
exchange can cope with. Besides, I think the limiting factor is safety
of engineers working at exchanges...

Philip.
Received on Wed Jul 22 1998 - 13:10:43 BST