Phone wiring

[DaveHerns]

Do we need to connect the 3rd bell wire when installing extension sockets these days ? I modified my wiring when changing from BT to Virgin .The Virgin chap said I only needed to run 2 cores from the master socket to the extension and it works but is it right ?

 

[sparkymarka]

Most modern phones don't need it.

 

[DaveHerns]

That's what he said . So why do we need master and slave sockets (or don't we) ?

 

[Europlex]

That's what he said . So why do we need master and slave sockets (or don't we) ?

Look inside a master & a slave and you will have your answer.

The master has components that let the Teleco test the line, these are not needed further on, hence, master / slave.

 

[plugwash]

Basically there are three things in a "BT" style master socket that are not in an extension socket.

Firstly there is the ringing capacitor. Historically phones in the UK relied on a ringing capacitor in the master socket rather than having their own ringing capacitor. I belive this was done to reduce loading on the line caused by multiple ringers. Either way it's a UK oddity and the modern global market means that many phones sold in the UK now use internal ringing capacitors rather than the one supplied by the telephone wiring. Also if you use ADSL with individual filters then it's the ringing capacitor in the filter that is used rather than the one in the master socket.

Secondly there is a surge arrester to reduce the chance of damage to equipment if there are surges in the phone wiring due to lightening (note: this WILL NOT protect against a direct lightning strike).

Thirdly there is a resistor between the ringing capacitor and the other side of the line, this allows for the line test systems at the exchange to detect whether the line is intact as far as the master socket or not.

 

[DaveHerns]

Thanks all,

I think I've worked out how to do this now . As long as we have one master socket on the system we can use 2 cores to link in the extensions

Dave