The Biddle 435F TDR is designed primarily for use on twisted-pair telephone cables, although it may also be used on multi-conductor control cables and power cables. It is unique in that, without any additional accessories, it can test a single line, compare a good cable pair with a faulty pair, balance a good pair with a faulty pair showing the algebraic difference, and transmit on one pair and receive on another pair to prove out splits and resplits.
The 435F can be used to identify and/or locate: opens, shorts, high resistance splices, wet splices, sheath damage, split cable pairs and resplits, water migration, taps, connectors, change of insulation, amplifiers, repeaters, load coils, stubs, and capacitor networks.