Old technology. No different than an acoustic modem.
LOL, it is all on the wheel man. What is old is new again!
I have to admit, I got a huge kick out of this one.
I have seen control signals transmitted over a string. Speaker on one end and a phonograph cartridge on the other. A string went from the speaker to the phono needle on the other. They were mounted in oatmeal containers. Thus, the "Oat-o-Phone" was born.