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1. The concept of fully reliable and secure communication facilities, completely separate from the power system, provides a new approach to problems of system design, relay protection, and system operations. 2. Initial tests demonstrate that microwave equipment can provide these communication facilities and that its use for protective relaying communications is practical. 3. Protective relaying by the use of microwave presents the following advantages: (a). No power system components or connections are used, with the following results: (1) The number of high-voltage components are reduced thus minimizing equipment failures which might cause customer outages. (2) Component failures need not cause circuit outages; stand-by equipment is practical and economical. (3) Maintenance of the equipment can be done without circuit outages. (4) Personnel and system hazards are minimized because of the reduced high-voltage switching for construction and maintenance needs. (5) The problem of additional space required for 1,200-ampere traps and for coupling devices as in carrier-relaying installations is avoided. (b). A new degree of freedom is available for integrating older parts of the system into new system requirements. (c) Multiterminal line-relaying problems are minimized and satisfactory system performance can be realized with microwave relaying from many system configurations formerly considered unsatisfactory because of relaying limitations. 4. The zone-comparison method can readily be applied to available types of relays and even existing relay installations. The control circuitry required is relatively simple.