From: Terry King
Subject: Re: Single / Multitone Detector (Not DTMF)
Date: Tue, 14 Jan 2003 12:41:24 -0500
Organization: Mountain ClockWorks
X-Newsreader: MicroPlanet Gravity v2.30.1784
> The most vexing problem with using what's built into the radio is that
> anyone with another radio and a little patience and good ear can
> duplicate the tones and bingo! turn on or open your whatever.
Thanks for the suggestions. Actually, I am in a VERY interference
free area, probably the darkest point in New England except
northern Maine. That's for all frequencies from Light down to
the maximum skip frequency. I only get interference from
ONE TV station, but I almost always just turn the set off and
do electronics instead. I've been monitoring for days on a typical
FRS channel and heard no-one. If I pick a CTSS frequency as well
I expect the risk is real low of anyone even knowing I exist.
I plan to have my existing system talk back, as of now, but
I'll probably set up some simple log-in sequence to validate
It's US. Hmmm. I can also disallow certain actions from this input,
but there's nothing that can 'blow up the house', although the
backup heating level can be changed. Mainly I just want to turn the
doggone lights on from 1000 feet away, so we don't have to try to
walk down a snowy road in the dark while loaded down with Groceries.
Yes: there SHOULD be a flashlight in everyone's car...
TECH issue: I had a suggestion that I may be able to detect these
signals accurately enough by just looking at Zero Crossings with
the PIC. I'll probably get to try that some, today. Anyone done
that, or similar approach? Signals SEEM to be actually single
tones, with several "warble - bleep" variations in frequency.
Thanks for the help...
Regards, Terry King ...In The Woods In Vermont