EXFO FTB-635 Wideband Copper and DSL Test Module - Manual (Page 224)

Signal Test
216 FTB-635
WB Balance Test
WB Balance Test
The wideband balance test ensures that the balance ratio for the twisted
pair complies with applicable standards so as to reduce the effects of
common-mode voltage to ground. The better the balance of the cable pair,
the higher the dB reading. Unlike VF Balance, WB Balance measures
balance across many frequencies to get an understanding of balance at
higher frequencies used for DSL. However, as frequency increases,
balance is reduced, so that a single threshold value across the wideband
range is an approximate indication in the test. Significant decrease across a
wide band of frequencies could be indicative of service affecting cable
fault affecting higher frequencies more than low (and hence DSL).