[Gllug] ADSL on BT phone wires

[Christopher Hunter]

On Wednesday 16 Aug 2006 14:24, Ryland, Peter wrote:

> Well, in the olden days of UK telegraphy and telephony, it used to run
> on a ground return system, meaning that you would only have one wire
> running to your home and the signal was grounded at each end forming the
> complete circuit.
>
> Considering a phone is only connected to the line and a modem is
> typically also connected to the power socket, and hence a ground, it
> doesn't seem too far fetched an explanation.

This was also the principle used for the "party line" system - one leg of the 
phone line was grounded to signal one subscriber, the other leg for the 
second subscriber.   The user obtained dial tone by pressing a button on 
their telephone, providing the ground connection.

Ringing was also ground referenced in some cases to allow separate ringing for 
the two subscribers, but seldom worked well.

The earth rod at the subscribers' house was crucial to the system, and a poor 
earth was often improved by the application of any liquid!  It was a 
temporary "fix" in dry weather!

Chris 

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