[aprssig] APRStt lives! (APRSspeak)

[Robert Bruninga]

> So rather than using PL tones, could we not do 
> something like using the DTMF key associated 
> with the last 2 characters of their call for 
> example?  So, since I am W5GGW, I would use 49?

Yes, the short-cut abbreviation is fundamental to the APRStt
concept.  The full callsign only has to be sent once.  From then
on, the abbreviated call is used.  But for normal use, it still
needs the overlay character to help resolve callsign duplicates
and it needs the checksum for reliabilty.  

The full callsign format as discussed before is AccccccccccccVK#

The abbreviated format is AnnnVK#

 Where A indicates it is a callsign
 Where nnn is the 1 key abbreviation of the last 3 call
characters
 Where V is the overlay character or numeral
 Where K is the checksum

Again, this is saved in DTMF memory just like the full callsign
so that it can be sent easily with just two key presses.  Its
advantage is that it is only 7 DTMF tones instead of 16.  And
for tactical events, the shortest tactical calls are 3 digit
numeric only with no overlay and no checksum.  Annn#

Bob, Wb4APR