[aprssig] Telemetry definition messages

[Andy AB9FX]

I tried to find how often should be sent telemetry definition packets. Is 
there any specific time?
I do some tests with new project called APRS Deluxe by Radek SQ2FOA. This is 
hardware unit working as tracker, wx station, digi, and more. Among many 
functions, one of them is telemetry. So far, five analog inputs are 
available. In the Deluxe could be specified name, units, and coefficients 
for every analog value. Monitor window displays all defined telemetry 
values. Moreover, name, units, and coefficients are sent as APRS telemetry 
parameter messages. So, every other station can know these telemetry 
definitions.
In current beta version, messages are sent every time, right before 
telemetry packet. I know this is not a good idea for regular work. So, we 
are looking for proper rules regarding telemetry definition messages. In my 
opinion, the best way would be special query to get them at request. But, 
there is no such query in the APRS specification.
My tests with Deluxe are under AB9FX-8 callsign (all tlm data without 
special meaning, just testing, except A2 - internal voltage) 
http://www.findu.com/cgi-bin/raw.cgi?call=AB9FX-8&start=24&length=24
AB9FX-8>APFOA0,WIDE1-1,WIDE2-2,qAO,AB9FX::AB9FX-8 :PARM.,,I,T,F,,,,,,,,
AB9FX-8>APFOA0,WIDE1-1,WIDE2-2,qAO,AB9FX::AB9FX-8 
:UNIT.LUX,V,A,DEG,HZ,,,,,,,,
AB9FX-8>APFOA0,WIDE1-1,WIDE2-2,qAO,AB9FX::AB9FX-8 
:EQNS.0,1.9255,0,0,0.1,0,0,1,0,0,1,0,0,1,0
AB9FX-8>APFOA0,WIDE1-1,WIDE2-2,qAO,AB9FX:T#013,048,047,049,051,053,00000000Test
Screenshots of Radek's project http://sq2foa.republika.pl/ (link - APRS 
Deluxe)
There is also a link to download project simulator running under Windows
http://sq2foa.republika.pl/deluxe_win.zip
After opening this program all navigation is available with arrows, Enter 
and Esc. Telemetry monitor window by Esc from main view. Example packets 
could be changed in the 'wynik.txt' file.
73!
Andy AB9FX