[hereforphone]

I think this relies on the particular string being a linear time-invariant channel. There is some limit where the string won't react accordingly (at a certain low or high frequency). What is that later phenomenon called, anyone know?

[NavinF]

Hmm the author had to use salt water to get it working. Maybe resistance is the limiting factor rather than dispersion. In which case a higher power modem or some sort of amplifier would get this working over >2m distances.