wire transmission

Wire transmission guides information-bearing electromagnetic waves along a conductor to a receiver, accompanied by electric current flow. This current is partially lost as heat due to the conductor's electrical resistance, causing signal attenuation that increases with distance.123

Early telegraphy used a single iron wire with earth ground for return conduction, suitable for low frequencies. However, higher frequencies, like speech, experienced significant attenuation, radiation losses, and interference from sources like lightning or crosstalk.1

To improve this, telephone systems adopted the open-wire pair, using two parallel copper wires for forward and return paths. This balanced circuit reduced sensitivity to distant interference. However, crosstalk between adjacent pairs remained a challenge, addressed by periodically transposing the conductors. Modern wire transmission primarily uses metallic-pair circuits, often with copper wire due to its low resistance and high strength.31