Digital communication channel interface

摘要: A differential protective relay system includes relays 19A and 19B at the terminals of a protected transmission line segment 21. Analog signals QL1 QL2 are sampled respective ends 21, digitally encoded using delta modulation biphase-mark encoding, multiplexed transmitted over 1.544 Mbps T1 communication channel 20 to other end where they decoded compared with local signal that end. Power is removed from if difference between remote exceeds predefined value. Biphase-mark encoding employed so clock may be recovered signals.