On 19 Nov 2006 17:40:18 GMT, (Andrew
Gabriel) wrote:

In article ,
Peter Parry writes:

CLI is passed in the UK between the first a second ring
as a tone burst and comprises only numbers.

That's how the BELL system works. BT sends the data before
the first ring, preceded by a line reversal.

You are absolutely right. I meant to mention both but got
distracted!

There's also
an off-hook signalling method which is used during call
waiting, but that requires that the phone indicates it can
take the data when off-hook, or it's not sent.

Has that ever been implemented? I was under the impression it wasn't
used (or it may just be that not many phones can use it).

--
Peter Parry.
http://www.wpp.ltd.uk/