maybe it might be best if I just make a longer cable, does anyone know the pinouts for the RJ11 plug at the Beocom 2400 end of the cable ?

link

For older phones to ring they use pin 3 on the extension which is produced from the capacitor in the master socket. So your extension cable must have pins 2, 3 and 5 connected.

trouble is there is no extension socket Keith, just the BT master, we are just plugging in a 10 metre cable reel to the BT master ( NTE ) socket on the wall, and using the cable supplied with the Beocom 2400, when only using the supplied 2 metre cable the phone rings fine, but when we use the 10 metre extension reel between the BT Master and 2400 it does not ring

BT Master -  10mt Cable Reel  -  Beocom 2400

As I said, that's because your 10 metre extension cable does not have pin 3 connected. Modern phones don't need it, but the 2400 does.

ah, so even though the BT Master only has pins 2 and 5 connected, the 2400 needs an extension cable that has 2, 3 an 5 on the RJ11 socket into the bottom of the phone

Keith, I just don't get it how it magically works with the supplied B&O cable if there is no wire even terminated on pin 3 inside the BT master socket ??