EXPERIMENTAL BIDIRECTIONAL SUBSCRIBER LOOP TRANSMISSION SYSTEM.

A COMPLETE HARDWARE IMPLEMENTATION OF AN EXPERIMENTAL TWO-WIRE DIGITAL SUBSCRIBER LOOP TRANSMISSION SYSTEM USING BALANCED PAIRS OF WIRES IS DESCRIBED. IT IS BASED ON THE TIME DIVISION BURST MODE TRANSMISSION SCHEME (PING-PONG), AND PROVIDES TWO INFORMATION CHANNELS, 64 KBITS/S AND 8 KBITS/S, AND A SIGNALING CHANNEL BOTH WAYS. THE BURST CYCLE IS 2 MS AND LINE TRANSMISSION RATE IS 192 KBITS/S. THE SALIENT FEATURE OF THE SYSTEM IS THAT IT IS EQUIPPED WITH A POWERFUL BRIDGED TAPEQUALIZER WHICH HAS THE CAPABILITY TO COMPENSATE A LARGE FRACTION OF EXISTING TWO-WIRE SUBSCRIBER LOOPS IN JAPAN. IT ISREALIZED BY A FIFTH-ORDER RECURSIVE FILTER USING ANALOG TAPPED DELAY LINES, AND A MODIFIED ZERO FORCING ALGORITHM IS ADOPTED FOR THE ADAPTATION OF THE TAP COEFFICIENTS. THE EXPERIMENTAL RESULTS SHOWED THAT THE COMBINATION OF THE ″ROOT″ F AGC AND THE BRIDGED TAP EQUALIZER ENABLES THE DIGITAL TRANSMISSION UP TO 4 KM ON THE 0. 4 MM ″PHI″ SUBSCRIBER LINE WITH THREE BRIDGED TAPS EACH OF 400 M LENGTH.