The general problem of control of the grid is outlined. Reference is made to the location and layout of the control buildings. Details are given of the communication system rented from the Post Office and of the special requirements with regard to its use in conjunction with the Central Electricity Board's system. The equipment of the control rooms, consisting of telephones and automatic indicating equipment, control desks, system diagram, frequency and time control instruments, is described.Reference is made to the general features of the telephone system and automatic indicating gear. Particulars are given of the various systems of remote metering employed. Concentration of essential equipment in a convenient form on the control desk is explained, with special reference to the desk at Bristol. Types of system diagram and frequency-control equipment are discussed.