From: Terry Pinnell
Subject: Re: Message Waiting LED on Simple Office Phone?
Date: Tue, 10 Sep 2002 08:02:20 +0100
NNTP-Posting-Date: Tue, 10 Sep 2002 07:02:25 +0000 (UTC)
X-Newsreader: Forte Agent 1.92/32.572
email@example.com (Bob Neidorff) wrote:
>The telephones in our office are simple phones, like the "2500"
>plain old touch-tone telephone, but they have one additional feature:
>a "message waiting" LED that flashes when the PBX tells the phone
>that there is a message stored in the PBX.
>What is the signal that drives this LED and what is the schematic of
>the LED circuit to detect this signal in the telephone? I'd like to
>add an LED to a non-LED phone and want to wire it the same way that
>it is the "normal" telephones, rather than "re-invent the wheel".
I had a similar requirement for home use, as raised in
A little later, on 30th Nov 2001, in 'Detect 'phone line status' in
I see I rashly wrote: "Breadboarding today, and will post result
Nearly a year on, the circuit I was developing remains only about half
complete, as I shortly afterwards got distracted with something else.
But the approach I summarised in that last thread still seems valid.
(If/when I master PICs, that could become another contender.)
Hobbyist, West Sussex, UK