APRStt HT TEXT DATA EXCHANGE!
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Before the entry of the Kenwood D7 into the market, several 
manufacturers had experimented with using Touch Tone signalling 
transmission and display in their handhelds.  These Handhelds 
can send AND receive short TEXT fields via Touch Tones:

Kenwood: TH-28A/48A/78A
Yeasu:   FT-11R,41R,51R
ICOM:    W31A

For users with these radios, APRStt can send them textual information
directly to the front panel of their radios.  The applications
are boundless limited only by the imagniation of the end users.
  
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MESSAGE TRANSMISSION AND RECEPTION
 
The TEXT that can be transmitted and received at one time can be
up to six characters long on the Kenwoods and 8 characters long on 
the Yeasu's.... but there can be up to 10 such text bundles.  This 
function is used with DTSS or Paging.
 
Message Reception
* Turn the DTSS or paging function ON.
* Press F then MSG key to activate message function.
* The radio can not receive any messages until you receive a DTSS
  code that matches to your  3 digit DTSS code. (say, "123")
 
incoming DTMF code
 "1"
 "2"
 "3" -> matches to your DTSS code -> waiting for header for 2 sec.
 "#" -> header for new message -> this code must be received with in 2 sec.
 "2" -> message body start
 "A"
 "2"
 "B"
 "2"
 "C"
 "#" -> terminate the new message
 
Notice that, DTSS or paging must be activated and user code matched.
 
Code Entry Chart
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Text characters are entered always as two key presses per character.
The first press indicates the key on which is found the desired
alphabetic letter.  This followed by either of four other keys to
indicate if it is the Numeral or the 1st second or 3rd character in
the three charactger group.  To get the letter M you would press the
"6" key and the "A" key to indicate that it was the first Key in the
"MNO" combination.  The following quasi graphic shows the
equivalents for each letter and numeral:

[1:1 Q:1A Z:1B _:1C]  [2:2 A:2A B:2B C:2C]  [3:3 D:3A E:3B F:3C]

[4:4 G:4A H:4B I:4C]  [5:5 J:5A K:5B L:5C]  [6:6 M:6A N:6B O:6C]

[7:7 P:7A R:7B S:7C]  [8:8 T:8A U:8B V:8C]  [9:9 W:9A X:9B Y:9C]

                      [0:0               ]

To Implement this in APRStt, the APRStt software keeps a list of the
DTSS codes for each callsign with the capability.  Thus, whenever
APRStt sees a message to a station with DTSS capability, it goes to
this table and converts the APRS message callsign to the correct
DTSS 3 digit code.  Then APRStt sends the tones over the repeater
to the DTSS HT user where the message is shown on his display.

All it takes is a little software!

de WB4APR, Bob