BT master socket change

The master socket in my uncle's house is a solid plate like the one at the top of this page.

I loosened the plate and saw an extension cable in the same terminals as the incoming telecom cable. It been like that for years apparently.

So the extension cable is on the same side of the master socket as the incoming cable with extension phone working along with ADSL broadband.

Should this be changed?
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I would guess one of two things here. One, the socket is an old-style master which pre-dates the NT5x (with removable lower plate). If the socket is smaller than a standard single socket at approx. 65mm x 65mm then this is the most likely.

If, however the socket is approx. 85 x 85 mm and fits a standard socket box, then the most likely scenario is that the NT5x had been damaged and replaced with a unit from the local DIY store.

I believe it is only recently that NT5E boxes have been available to purchase. Perhaps others can confirm/deny this.
Take the wires out of terminal 3 and you'd have the same effect as one of the new nte5s.
The house my uncle lives in is 32 years old and the master socket is the original.

Since the extension sockets are wired to the same terminals on the master socket as the incoming telecom cable, I'm wondering how they are working properly when they are on the wrong side master socket electronic components?
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The A and B wires from the exchange go via the terminals in the master socket to the telephone sockets pins 2 and 5. So the telephones can be connected to the A and B wires anywhere and either before or after the master socket. In fact provided the phone has an internal bell capacitor there is no need ( electrically ) to have a master socket.

The master socket provides a place for the bell capacitor to be fitted between wires 2 and 3 to allw AC ringing voltage to reach the bells in phones that do not have internal bell capacitors. It also contains a resistor used for line testing and an over voltage transient absorber.

It also provides the demarcation point between BT owned lines and the customer's internal wiring.

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