This week I found myself looking into a phone line issue. I used to deal with a lot of these. This post aims to provide a reminder of useful numbers to use when diagnosing a UK phone line issue.

For these events, I always try to have a small analogue phone handy to test the line.

Old shortcode numbers

These numbers work on older (e.g. System X) exchange equipment. Kept here in-case new ones fail.

174 – Noise and Ring Back Test
Dial 174, once it is picked up, hang up unless you want a silent line for a noise test (the line will be silent). The exchange will call you back automatically once you hang up. This still works on modern infrastructure.

175 – The SALT (Subscribers Automatic Line Test)
An exchange based line test

177 – Confirms your phone number

New shortcode numbers

150 – BT Residential Customer Services

152 – BT Business Customer Services

17070 – Line test service, replacing 174 and 175 (confirms phone number before menu options). This number should work on all networks (Openreach, Sky and Virgin Media), although the options given will be different. Openreach menu options are below.

1. Ringback
   Calls the CLI back, to test the line. This option will not appear if your CLI is blocked. Dial 1470 before 17070 if your line blocks it’s number by default.
2. Quiet line test
   Line will go silent so you can hear any noise on the line.
3. Fast test
   Does a basic line test (testing the line from the exchange to the master socket). Note that the test equipment is separate equipment in the exchange, so if your issue lays in the exchange, this test may miss it.
4. Fast cleanse
   I’m not sure at this time what this option does.
5. Clear down
   Hangs up the call (can be used to exit the call)

To identify the line provider, call 150 for customer services and see what company it is.

Call barring details:

Openreach: https://kb.needmoretime.co.uk/BT-Telephone-Short-Codes-Including-Divert-Codes.html

Virgin Media: https://kb.needmoretime.co.uk/Virgin-Phone-Formerly-NTL-Telephone-Short-Codes-Including-Divert-Codes.html

You can try calling Residential Customer Services (150) or Business Customer Services (152), or any 0800 number. These should all work from a barred line.