A. They indicate splices, water in the cable, split pairs, and discontinuities or faults.
B. Do not connect live circuit cables to the input of the time domain reflectometer. Connect the cable that is being tested to the cable connector on the front panel of the time domain reflectometer.
C. Upward deflections indicate high-impedance mismatches or opens, and downward deflections indicate shorts or low-impedance mismatches.
D. They are used to select the I/O impedance of the time domain reflectometer. You can select 50, 75, 95, or 125 impedances.