Some features of half-wave and full-wave transmission lines are considered. Transmission of power is possible by a line of any length, but with inadmissible flows of reactive power. High transmission line efficiency is achieved when a line is a little longer than half-wave. The line is assumed to have at its ends devices for maintaining voltage and excluding the influence of the power system network impedances. It is shown that power which is much greater than the natural value can be transmitted with high efficiency when the transmission line end voltages are markedly lower than the voltages at the middle of the line.