From Len Mann
I was intrigued by the benefits Ian Stewart suggested may follow from using Euler’s mathematical ideas (24 March, p 48). However, the proposal to use electricity power cables to carry data signals has been in development in one form or another for at least 20 years. The odd trial installation has connected real homes, and error correction and other techniques can indeed get over the problem of data corruption.
A more intractable problem lies in the signals that escape from the wires. If every home were wired up in this way, our airwaves would fill with unwanted and interfering signals, upsetting our radio, mobile phones and even television. One way of minimising this would be to spread the signal across a wide band of frequencies, trying to keep the signal level within the background noise levels; but there is a fine balance between enabling the signal to get through and radiating it into the air at too high a level.
No one has yet solved this problem. The idea has anyway been overtaken by modern wireless technology.
Gerrards Cross, Buckinghamshire, UK
