SSID

An SSID is a number added after the callsign to indicate the function of the station. SSID assignments are slightly different for Winlink and APRS:

SSID	Packet, Winlink, etc	APRS
-0	Home station.¹⁾	Your primary station usually fixed and message capable
-1	Home station personal mailbox.²⁾	generic additional station, digi, mobile, wx, etc
-2	Gateways	generic additional station, digi, mobile, wx, etc
-3	Full service BBS's.³⁾	generic additional station, digi, mobile, wx, etc
-4	Network Nodes.⁴⁾	generic additional station, digi, mobile, wx, etc
-5	Console, keyboard or printer	Other networks (Dstar, Iphones, Androids, Blackberry's etc)
-6	Conference Bridges	Special activity, Satellite ops, camping or 6 meters, etc
-7	Crossband digipeaters and KA-Nodes	walkie talkies, HT's or other human portable
-8	Crossband digipeaters	boats, sailboats, RV's or second main mobile
-9	Mobiles	Primary Mobile (usually message capable)
-10	Winlink 2K	internet, Igates, echolink, winlink, AVRS, APRN, etc
-11	unassigned	balloons, aircraft, spacecraft, etc
-12	unassigned	APRStt, DTMF, RFID, devices, one-way trackers*, etc
-13	unassigned	Weather stations
-14	unassigned	Truckers or generally full time drivers
-15	Downlink address when exiting the far end of a network connection.	generic additional station, digi, mobile, wx, etc

Sources

¹⁾

Note: “-0” not needed - automatically presumed if no SSID.

²⁾

Usually a TNC-based PBBS

³⁾

Those that forward mail and bulletins

⁴⁾

Having two or more radio ports that perform routing functions via TCP/IP, NetROM, etc. Can be combined with BBS's that also perform routing.