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Re: APRS Touch Tone signaling



I had written about APRStt (A universal Touch-Tone to APRS message
conversion system letting anyone with any radio or HT enter Email and
worldwide APRS messages):

> > The TTone sequence of *33*20480602803333 from ANY HT, gets converted by
> > APRStt software at the repeater to this 144.39 PACKET::
> >
> >    WE4APR>APRS,WIDE::EMAIL    :bruninga@maile.earthlink.net Get me at 3.

Someone asked:

> OK, I've got to ask, how on earth does a 18 character touch tone sequence with
> only 4 bits per character decode to an almost 70 character ASCII string?

Thanks for asking..  It is really just an abbreviated form of the existing
APRS-to-Email message format:

1) The * means it is an APRS message
2) The 33 decodes to the TOADDRESS of the single letter "E" which the
APRStt parser will recognize as a shortcut for "EMAIL"
3) The next * separates the TOCALL from the MESSAGE
4) Now, knowing that it is an Email, APRStt looks for the next digit to
tell  APRStt which individual's EMAIL address in your own personal list of
up to 9 Email address should be used for this message.  In this case, the
number 2 person on my list is bruninga@maile.earthilink.net
5) The remainder of the TTone sequence  0480602803333 decodes exactly
as this " gt m at 3" which APRStt interprets as "Get me at 3"

APRStt has a standard definition for many commonly used single and dual
letter combinations.  Knowing that these are being entered by a TTon pad,
it is easy to assume that they are abbreviaitons.

> BTW, anyone wanting to do this on my repeater will be told NO WAY.  Even with
> touch tone muting, it's still obnoxious.

Different strokes for different folks.  Probably might get used once a day
by someone traveling that wanted to send an EMAIL message while stuck
somewhere with only his HT.  No worse than an Autopatch.  In fact, it
takes FAR less time  than an autopatch.  That entire sequence can be sent
in under 3 seconds if keyed into a TTone buffer on the HT before
pressing the PTT..

Oh, what was mising from the above sequence was the MYCALL of the sending
station.  If you look at the APRStt spec, the MYCALL is only a 3 digit
hash of your callsign suffix.  Mine would be 277.  If 3 digits resolves to
an ambiguity between two or more users of the same hash code at your
repeater, then the repeater tells you that and you have to enter more
digits until it recognizes your call.  But from then on APRStt knows who
you are.  APRStt being software can do a lot of heuristics to fill in full
human readable text conversions for quite abbreviated sequences...

See the APRStt WEB page.  http://www.ew.usna.edu/~bruninga/aprstt.html

de WB4APR, Bob


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