ALL CAPS predates Teletype use. Radiomen copied Morse using a “mill” typewriter with no shift needed - all caps, a 1 key, and a slashed zero. So all messages were in ALL CAPS format with no confusion between O and 0 or 1 and L.
When the change to upper-lower case came, the Wall Street Journal ran an article, illustrating it with a drawing of a MITE. I was disappointed it wasn’t a M28, but they probably wanted to save column inches.
Drawing
Mill typewriters and a downloadable font for your computer
Cheers
Nick
The navy was still using ALL CAPS to send messages up until 2013!
Not sure but I think this practice had it roots in Teletype.
Maybe Nick can explain that one.
-Steve
