[Gllug] Multiple phones on a home network with single router

James Roberts j.roberts at stabilys.com
Fri Mar 18 11:46:22 UTC 2011


On 17/03/11 23:45, t.clarke wrote:

Nice diagram:

> I have three sockets (all 'masters' as I couldn't be bothered to fiddle around
> with the extra wires to support ringing on the 'extensions')  with two of them
> spurred/daisy-chained off the back of the master socket:
> BTline>----+Master----filter--Phone1
>             |
>             +--<40feet>-------socket2-----------socket3
>                                  |                 |
>                                filter            filter
>                                |   |               |
>                            Phone2  ADSL         Phone 3
> and the arrangement works fine     (7.6Mbps download)

But really it's like this:

                               |    |             |
                            filter  |          filter
                               |    |             |
                           Phone2  ADSL         Phone 3

The point being, many of my clients (and colleagues!) have not 
appreciated that the filter is only to remove radio frequencies for the 
phone (I don't imply that of the author!). The revised diagram makes 
clear that no microfilter or any other sort of filter is needed for the 
*DSL signal.

Unfortunately micro-filters are of varying quality (low -> lower in my 
experience) and so the *DSL signal is in fact attenuated by the parallel 
presence of multiple filters on the line.

This is of course  why (as many have pointed out) it is much more 
effective to have a single high-quality filter at the entry point to the 
premises, with that filter feeding all the phones.

 > I have never understood why a few extra feet from the master socket
should make
 > any real difference if the sockets are properly filtered;  bearing in 
mind that
 > the extra few feet are a fraction of the total line length.   The big 
 > I have found is the quality of the microfilters (I have had some 
crappy ones
 > in the past  - it is worth buying good quality ones and avoiding the 

On the *DSL side, I have frequently had to use long runs (<= 30m) of t/p 
cable feeding the *DSL signal to modem, with no problem or significant 
measured signal loss.


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244 Kilburn Lane
W10 4BA

0845 838 5370
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