[aprssig] station capability flags

Jason Winningham jdw at eng.uah.edu
Wed Feb 28 17:21:07 CST 2007

There was some discussion in the past few days about not knowing  
which stations were acting as Igates.  One thing that has always  
seemed missing in the APRS protocol is a way to indicate station  
attributes.  Selecting an icon is quite restrictive.  What if it's a  
digi with a weather station, or emergency power, or an Igate, or all  
of the above?  How you you indicate more than one, without doing  
network traffic analysis?

In the absence of a dedicated field added to the protocol, it seems  
to me we could get a very limited set of flags by using the TOCALL  
SSID bits.  A quick scan of my tnc log file didn't show any TOCALL  
addresses using an SSID other than 0.

One approach would be using the 4 bits to flag the 4 most useful  
attributes that may not be indicated by the station's icon.

Another method, more complex, would be to define 15 common sets of  
attributes indicated by the non-zero SSID.


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