This paper discusses the special factors to be considered in designing an interconnecting link between two alternatingcurrent power stations, with particular reference to power factor and power factor control.Equations are given in the Appendix for determining the power factor of the line current with any given load and voltage boost, and the voltage boost required to transmit any given load at a given power factor.The three possible conditions of voltage relationship between the power stations, and their effect on the power factor of transmission, are stated.Various types of booster for controlling the power factor are discussed.The effect of power factor variation is pointed out, and the desirability of fully considering and deciding on the power factor of transmission before installing a line is emphasized.Tables are given to illustrate the effect of transmission power-factor on the cost of transmission and on station power-factors.The synchronizing power of the line is briefly discussed and its value is worked out in the Appendix.