[aprssig] APRStt (APRS touchtone DTMF)

Robert Bruninga bruninga at usna.edu
Fri Sep 19 15:44:35 CDT 2008

> How are you going to differentiate the DTMF 
> tones used for this from the repeater control tones?   

Good questions.  I have tried to get people who know these codes
to provide the best recommendations.  Best we have come up with
is to begin each APRS string with ##A or ##B or ##C depending of
the APRS application.  The ## in many repeaters tells the
repeater to ignore the following tones.  THen two of them
improve that probabilty of detection.  The A or B or C indicates
the type of APRS code to follow...

> 1. Most repeater owners who use DTMF control 
> guard them very  carefully.  One wrong tone can 
> cause the repeater to go crazy, meaning you 
> might have make a trip to a mountain top 
> or restricted access building.  They are not 
> universal, and many poeple will be suspicious 
> if you ask for them out of the blue. 

Yes, only the existing repeater sysop knows if this application
will be good on his repeater or better to be placed elsewhere.
There are so many unused repeaters, that there are plenty of
places to put them.  Actually, APRStt was mostly designed for
its own frequency at an event or special purpose.  It should not
be placed on a repeater that would have problems for it.

> 2. Some repeaters strip DTMF off, others do not...
> 3. How will I know if a repeater in an area 
> uses this? Is  this going to be in ARRL 
> repeater directory, or sent on APRS?  

Yes, it will show up on every APRS map, or FINDU, or whatever.
The APRStt engine will appear on all maps with its special
APRStt symbol and frequency so that everyone can tell where it
is...  But of course the DTMF user doesn't see the local APRS
map, so you are right, it will be in directories, and it should
be included in the voice announcement.

> I don't think you want to just blindy try 
> sending DTMF on a repeater without asking 
> a local user. 

Yes, that is a big concern.  These are all issues we need to
deal with, but at least now finally we have the mechanism.  Now
we see how to implement it..

Glad to have you on board and helping...


> Re: [aprssig] APRStt (APRS touchtone DTMF)
> > > APRStt coming soon!
> > 
> >>  but this will be a new version that
> >> runs under windows using only the sound 
> >> card for both DTMF decoding and Voice-Back synthesis.
> > 
> > Ehhh...is this going to be available on platforms 
> > that are suitable for unattended operation? (sigh)
> See www.aprs.org/aprstt.html
> Bob, WB4APR

More information about the aprssig mailing list