--- In 56solo@yahoogroups.com, Oliver Roberts <oliver@...> wrote:
>
> . . . Apparently, TalkTalk's Caller ID system is supposed to be
> identical to BT's, but there are some minor differences (not just the problem
> that I'm having).
>
> It's a strange problem because it works about 50% of the time on average with
> the Solo, and 90% of the time on a BT Freestyle handset. Probably everybody
> here knows the tell-tale "click...click" that the Solo makes directly before
> the phone starts to ring, and before it starts to announce the phone number.
> With my BT line, this was always a fixed "click...click", but with TT
> sometimes it doesn't click at all and as a result picks up no Caller ID at
> all (yet, the BT Freestyle does still display the Caller ID most of the time
> when this happens). . . .

A guess is that Solos click on BT lines because of either the line reversal that
heads the
calling line identification presentation (CLIP) signal or some other big change
in line
voltage. Often my Solo clicks when I take my handset off hook; sometimes it
clicks
without any call coming, perhaps when a neighbour takes their phone off hook.
The CLIP
data stream after the line reversal should not cause the clicks.

IIRC BT uses line reversals as part of the signalling to switch lines from idle
to loop states
at the start of a call. This is part of the prompt to our kit (e.g., Solos) to
receive CLIP data.
The CLIP data arrive before the rings. Our kit must have programmed delays to
pass the
CLIP data to our software between the first and second rings, when most comms
software
expects. Call Waiting signals seem very similar, but there is no line reversal
or switching
out of loop state.

Maybe TalkTalk does without line reversals along its local loop unbundled lines
to signal
an imminent CLIP, instead working rather like Call Waiting: hence lack of
clicks. TalkTalk
may even send the CLIP between the first and second rings, as happens over most
of the
world, even if the CLIP otherwise follows BT protocols. This may make TalkTalk
Caller ID
unreliable with a Solo, while other kit may be more tolerant, perhaps if it can
also receive
Call Waiting signals.

Sources:

Caller ID FAQ
<http://www.ainslie.org.uk/callerid/cli_faq.htm>

Wikipedia
<http://en.wikipedia.org/wiki/Caller_ID>

BT Supplier Information Notes 227 and 242 (PDFs, each 34 pp., available via
search)
<http://www.sinet.bt.com/>

£0.02

--

Laurence Taylor