Remembering years ago there was a 3 digit code that you could punch into the keypad and just at the second the long tone appears on the phoneline you put down the reciever and the phone will ring, i believe it was 174.

the engineer came round to test my line last week and did the engineer ring test using the above method but has the number changed as i cannot get it to work now.

17070 and press 1 then hang up or 1475, the call will ring then hangup on you - wait and it will ring back (deletes last called info on 1471) if you withold your number you will need to add 1470 first.