High Quality Content by WIKIPEDIA articles! High Quality Content by WIKIPEDIA articles! The telegrapher's equations (or just telegraph equations) are a pair of linear differential equations which describe the voltage and current on an electrical transmission line with distance and time. The equations come from Oliver Heaviside who in the 1880s developed the transmission line model which is described in this article. The theory applies to high-frequency transmission lines (such as telegraph wires and radio frequency conductors) but is also important for designing high-voltage energy transmission lines. The model demonstrates that the electromagnetic waves can be reflected on the wire, and that wave patterns can appear along the line.