The ADTRAN OCU Dataport Plus with Performance Monitoring is used for DDS and Switched 56 digital transmission over a 4-wire loop with up to 45 dB of loss. This unit adds intelligence and comprehensive DS0 performance monitoring to the industry standard WECO D4 channel bank and utilizes advancements in VLSI and customer-integrated circuit technology to provide all-rate capability and real-time error reporting in one low-cost dataport. Automatic adaptive equalization is employed, permitting reliable reception of low loop signals, eliminating the need for loop repeaters in many installations.