Andy Burns has brought this to us :
Harry Bloomfield wrote:

Dave Liquorice wrote:

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?

Your voip provider should (must?) provide a method, often called your E999
address

I have a normal landline number, rather than voip.