ATDT relief
I once wrote a program to send data for free anywhere in the world, by dialing another machine and then hanging up.  The remote machine's modem would say RING.  With the right excruciatingly adjusted and slow timing you could send binary data insanely slowly.  Start bit, then 8 data bits, maybe check bit, something like that.  Let's just say it never took off.  Something on the order of 0.1 baud.