That's a different implementation from DoD's classic AUTOVON system, which used phones with the "missing" four DTMF tones to assign priority. "Flash Override"

That's a different implementation from DoD's classic AUTOVON system, which used phones with the "missing" four DTMF tones to assign priority. "Flash Override" was pretty much restricted to National Command Authority (the President and Joint Chiefs) and would allegedly clear entire trunk lines to ensure call completion. https://en.wikipedia.org/wiki/Autovon https://en.wikipedia.org/wiki/Autovon