The loop pair-gain system provides an alternative to the traditional cable and structure design of the subscriber loop plant. As low-cost digital transmission technologies continue to emerge, their application in the subscriber loop plant has grown substantially and has found many different uses. The SLC-96 system [1] is a new, versatile pair-gain system handling the broad spectrum of telecommunication services needed to meet the widely varying requirements of today and the future, for both voice message and voice and data special services.

The residual transmission deviation of the L5 repeatered line can be divided into two categories, static or time invariant and dynamic or time variant. The static deviation, which is due to design limitations and manufacturing deviations of the basic and regulating repeaters, is compensated for by manually adjustable equalizers designatedE1andE2. These equalizers are composed of 28 Bode bump networks whose gains are adjusted to minimize the total mean-squared error of the transmission channel. The residual dynamic transmission deviation, caused by temperature variations of the basic and regulating repeaters, is corrected continuously by an automatic equalizerE3. The time-varying transmission deviations are detected by four pilot tones spaced across the L5 frequency spectrum. Four electronically controlled networks in the equalizer respond to the pilots to correct the dynamic transmission deviations.