Application of 720-cycle carrier to power-distribution circuits

LOW-frequency carrier has been applied extensively to distribution circuits for remote control of street lights, window lights, off-peak water heaters, and similar services. Since carrier makes available a control system whose operating flexibility can be duplicated only by the use of a number of separate wire or pilot circuits, it permits saving large amounts of copper and other critical war materials. The necessity of reducing illumination or “blacking out” lighting circuits under war conditions has emphasized the value of the direct control provided by a carrier system. More recently the importance of carrier control for air-raid sirens and for signaling air-raid warnings to defense centers and civilian-defense personnel has been demonstrated.