Funny story, right around the time the first one was published(a bit after but I didn't know about it), I was at my first job and I was tasked with doing a bunch of drivers for fiscal printers for linux. Saying that their documentation was crap would be a huge understatement. I.e:
0x4e -> next
0x03 -> cursor
And around 2 pages of addresses and single word descriptions. That was it. It took me 2 months of non-stop brute forcing to figure them out but eventually I figured them out. One of the things they could do is play sound and the test to check if they work when the technicians were installing them was to play the imperial march. When I showed it to the technicians, one of them said "Oh, you copied the floppy drive guy?"
I had no idea what he was talking about until he showed me. Lesson learned: it's the internet, you are never the first.
One little known feature of linux is that there are ANSI sequences you can send to the console that turn off and off the PC buzzer and alter the frequency.
One innocent use I used for this once was when I set up an on-demand modem system using ISDN for the office. If it detected a packet for off-site, it'd start the modem dialing and when the link was up, it'd make a series of ascending tones and after a minute or so of inactivity, it'd take down the link and play some descending tones. People tried not to use the internet unless they heard the ascending tones, so we only used a couple of hours of dial-up per day.
One not so innocent use for this was trolling the phone engineers who were tasked with installing something in the rack in the corner of the office. Every time they went round the back of the rack and touched anything, I'd make one of the servers beep, but always a different one and only when they touched a wire. Occasionally I also ejected and then tried to mount the CDROM, so they'd just hear a thud every now and then too. They literally had no idea what was going on and got quite paranoid every time they went to touch anything.
0x4e -> next
0x03 -> cursor
And around 2 pages of addresses and single word descriptions. That was it. It took me 2 months of non-stop brute forcing to figure them out but eventually I figured them out. One of the things they could do is play sound and the test to check if they work when the technicians were installing them was to play the imperial march. When I showed it to the technicians, one of them said "Oh, you copied the floppy drive guy?"
I had no idea what he was talking about until he showed me. Lesson learned: it's the internet, you are never the first.
But damn, this is impressive.