Autovon used "standard" Touch-tone phones. Ones with *all* the buttons. including the 4th column of 4.
Autovon actually made use of those 4th-column buttons, for things like indicating the 'priority' of the call. If all circuits were busy and you had "priority' traffic, you could push the magic button for that, as part of dialing the number, and some (random) "non-priority" call would get abruptly terminated, to free up the required circuit, so that your call could go through.
There were other 'specialty' capabilities as well, specific to a "command and control" operation.
The 'enhanced' features (including 'priority') were not necessarily available on -every- Autovon phone -- it took a certain 'class of service' as it were, before one could use them. And, of course, there were very specific 'policy' rules about _when_ one could use them.
[TELECOM Digest Editor's Note: As Robert knows, those four additional touch tone keys were known as A,B,C, and D. I forget the exact meaning of each, but my question is, did anyone with 'regular' service but with an Autovon phone ever try pressing those keys in a regular call? I did a couple times, and the immediate result was a 'fast busy' signal; the call would not complete. PAT]