5 bit is what radio amateurs call RTTY ...
5 bit code is Baudot (as in Emile Baudot, the guy who invented it). It
predates both ASCII and EBCDIC and was the standard for the wire services
way back when they used real Teletypes connected by leased phone lines. But
you're right - Baudot is the standard for radio teletype as well - hams are
poor and they bought all the surplus TTY equipment from the wire services
when they upgraded.
Although these days there are many ham digital protocols based on ASCII,
and most all hams have PCs. Not many actually use teletypes anymore...
Bob WU6V