BT, broadband and electromagnetic noise

[Noreen]

Interesting article here http://community.zdnet.co.uk/blog/0,1000000567,10007513o-2000331761b,00.htm

[Rik]

I can't help but feel that continuing to tell people to remove the ring wire will be simpler.

[kinmel]

I can't help but feel that continuing to tell people to remove the ring wire will be simpler.

too true

[Rik]

 

What's the betting that they just disconnect or remove the terminal on this i-Plate?

[Simon]

If this ring wire isn't any use, and interferes with broadband, why do they put it there in the first place?

[plugwash]

On almost all phone systems the ring signal is a low frequency but relatively high voltage (about 100V or so IIRC) signal on the phone line. This is seperated out from the DC line current by a capacitor and used to power the phones ringer.

For various historical reasons that aren't really relavent anymore BT decided (unlikely most other phone networks) it was better to have one ring capacitor in the master socket than to have a ring capacitor in every phone. While many newer phones have thier own ring capacitors there are still a large number of phones in use that do not.

With ADSL the ring capacitor in the master socket becomes redundant since to stop the ringers from interfering with the adsl the ring capacitor that is actually being used needs to be on the filtered side. As such all DSL filters contain thier own ring capacitors.

However the capacitor in the master socket while redundant is of course still there. Furthermore if you used the quick and dirty method of installation (that is you just plugged in microfilters to each phone socket without any modifications to the fixed wiring) there is still a load of wiring attatched to the line via that capacitor. This is bad for the high frequency performance of the line.