Re: Modem Caller-ID question (long-ish)

[James Derrick <james@xxxxxxx>]

On Thu, 16 Nov 2000 08:49:16 -0000, you wrote:

>If a Caller ID device was affected by a line reversal it would either
work
>or not work.
I tend to agree- if the fault were something as permanent as a wiring
fault then it shouldn't be intermittent.

For a bit more on how Caller ID works, there is a copy of the spec
("Suppliers' Information Notes" on BT's WWW
http://www1.btwebworld.com/sinet/
http://www1.btwebworld.com/sinet/242v2.pdf

The line state timing diagram on page 8 shows a line polatiry reveral
as signalling the start of the CLI. Could it be that the hardware is
more sensitive to one polarity than the other, especially if the bell
wire is disconnected (removing a different reference voltage) as the
cli_faq.htm document suggests?

I'm just clutching at straws really, but would be tempted to try the
mod before buying a Sportser Message Modem.


James

PS #include <standard disclaimer about BABT approval & no user
servicible parts inside>
---
James Derrick    james@xxxxxxx, Cramlington, Near Newcastle, England
Forwarding Service: jderrick@xxxxxxx
Beyond the Horizon of the place we lived when we were young,
In a World of Magnets and Miracles. Pink Floyd.

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