[aprssig] APRS User Activity Bit

[Robert Bruninga]

> Is there anything in APRS that would indicate stations 
> a user can communicate with? 

Yes, in APRSdos, all stations that have message capability
show up in bright white.  All others are a grayish (or other
colors dpending on the 8 other atributes).  This is determined
by the position format byte: Using the @ or =  (or a D7 or 
D700 Mic-E) signals it as messgage capable.  All others are not.

>This all came to light with a newbie asking the question, 
>"How or can I know, who has a keyboard that I can talk to?"

Ah ha!  In 2000 or so,  I also introduced the "ACTIVITY" bit.
This bit indicates if there is a human at the PC by detecting
human activity.  If the human is present within the last 10 minutes
then the N/S byte is in UPPERcase.  If that person's PC
detects no activity in the last 10 mintes, then the N/S byte is 
transmitted in Lower Case.

All APRS versions except UIview and APRS+SA can receive
the lower case N/S byte just fine.  But I think only APRSdos 
and maybe Xastir or APRSscs then have the option to 
"display only active stations"...

This feature we moved to the  APRS1.2 update list...

Bob, Wb4APR