Telephone Master Test Socket

telephone engineer essex nte5

Telephone Master Socket

A Residential  new telephone line installation should come with a single master socket or line box into the premises, which is provided by BT Openreach.

This socket is the demarcation point between the customer-owned wiring and BT Openreach network wiring.

The Telephone master socket can be referred to as an NTE5, which means Network Termination Equipment.



BT Openreach Testing Point

For households with the NTE5 telephone master socket, the demarcation point is actually within the socket.

The lower half of the face plate is unscrewed and removed. This exposes another telephone socket which is known as the testing point.




The permanent wiring on the telephone master socket, remains the responsibility of the service provider.


Until recently, this socket contained an enclosed spark gap, SP1, that could safely flash over internally to provide high voltage surge protection.

This component is no longer used due to negative effects on VDSL, ADSL, FTTC broadband speeds.

The socket includes a 1.8 µF capacitor (bell circuit) to feed the AC ringing and a 470 kΩ resistor (R1, out-of-service resistor) to permit remote testing when no telephones are plugged into any sockets.

Additional internal extension (secondary) sockets are wired off the master socket using the IDC system(Insulation Displacement Connect).



Telephone Master Test Socket Faults


So before you call your service provider follow the checklist:

  • What kind of fault do you have? Noisy crackling line, No Dial tone, No broadband, Slow broadband
  • Do you have a master test socket NTE5
  • Unscrew the lower half of the socket
  • Now test! Is it still noisy crackling, no dial tone, no broadband, slow broadband
  • If the answer is yes then call your service provider.
  • If the answer is no then call your local Telephone Engineer Essex.

Ex BT Openreach Telephone Engineer Brentwood 01277 287 077