On Sat, 06 Jul 2019 20:36:01 +0100, Harry Bloomfield
wrote:

Dave Liquorice formulated on Saturday :
Advantage of a landline (or VOIP number) is that you can register
your address and that pops up on the 999 operators screen.

How does one register one's address?

For a normal plain telephone line you don't. It is entirely
automatic.

As soon as the call is made the BT emergency operator will be shown
the call location. It matters not if you have chosen not to be in the
phone book or have your number withheld.