This standard describes the interconnection details for N@ where N = 1@ 2...12@ times 64 kilobit per second connections of teleprotection equipment to digital multiplexers using optical fiber. Requirements for both physical connection and the communications timing are also included. Purpose The purpose of this standard is to allow the interconnection of different vendors' teleprotection equipment with different vendors' multiplexer equipment@ without any restriction on the content of the N times 64 kilobit per second data using up to 2 km of 50 or 62.5 micrometer multimode optical fiber.