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[aprssig] DTMF encoding

Robert Bruninga bruninga at usna.edu
Tue Sep 30 22:05:28 UTC 2008

More ideas... I just re-read a note I got from
Jonathan(echolink) months ago and IRLP decoders do not decode
the "D" key.  SO maybe we could end the callsign with # just
like Echolink and other phone systems do.   Also, since Echolink
begins the call with "C" instead of my "A", I suppose we could
change all of APRStt...  To be Cxxxxxxxxxxxxx#

This more or less abandons the Kenwood D7 and D7XX formats for
APRStt, but then they don't need APRStt since they can key in
info directly into APRS.

> -----Original Message-----
> From: aprssig-bounces at lists.tapr.org 
> [mailto:aprssig-bounces at lists.tapr.org] On Behalf Of F5SMZ 
> Jean-Philippe
> Sent: Tuesday, September 30, 2008 5:38 PM
> To: aprssig at lists.tapr.org
> Subject: [aprssig] DTMF encoding
> Hi all,
> following the various posts today, here is the my
> 1) First, it appears that we need to stay below 17 digits 
> (e.g most of TRX have a 16 digits memory bank limit)
> 2) We need a standard DTMF keyboard layout (GSM/Yaesu 
> keyboard is fine; or at least more "standard")
> Here we go:
> Let's assume we use an encoding system "a la " Echolink; it 
> will lead us to a maximum of 12 digits for a 6 character
> Example: F5SMZ = 3350746194
> We need a checksum after that: 3350746194K
> and a "D" to terminate the sequence: 3350746194KD
> Now suppose we skip the ## preamble and just include the 
> leading A: A3350746194KD
> We have now a 13 digits sequence; in case we have a 6 
> characters callsign, we reach 15 digits, which is still below 
> the 16 digits memero bank limit of most TRX.
> This let us also run the B, C and Q APRStt sequences in the
> Hope it's help.
> jean-philippe F5SMZ

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