> This had a major denial of service security implication in that it would lead to the modem hanging up the connection should the computer ever try to transmit the byte sequence +++ATH0 in data mode.
Does this mean you couldn't send the documentation for the modem using the modem?
Still useful to know if you have a cellular hotspot. GSM uses AT commands for lots of things.
> M0 or M Speaker Mute, completely silent during dialing M3 is also common, but different on many brands
As a teenager with my first modem (I think I started with a 14.4, so not that early) I had no idea how to mute the modem with those commands yet while connecting to BBSes.
So I created my own "mute" (for during connection negociation at the beginning of a call, the modems were extremely noisy) system...
Late at night, when my parents were asleep, I'd unscrew the cover of the modem, take the PCB out and muffle it between two pillows while the connection was establishing.
Worked flawlessly.
As I was both up to no good and because I didn't want risking shorting the PCB, I'd then put the cover back on. Rinse and repeat every night.
That's funny. I clicked on the HN article on the home page about the AT Protocol[1] expecting an article on the Hayse set. And then I scrolled down and saw this article.
[1] https://news.ycombinator.com/item?id=49527123