Analog and digital subscriber-loop breakdowns can be quickly isolated with the xDSL-200 handheld transmission line tester, which enables telephone field engineers and technicians to perform narrow-band, wide-band, and DMM testing. Testing can be done on 2-wire, 4-wire, leased or dial-up circuits for use with analog, Pair-Gain, ISDN-BRI, DSL, HDSL and DDS equipment. The unit's One-Rotary-Selector design allows the user to pick a specific test or function with a flip of the wrist. Turning the selector to TX provides specific tones, while selecting RX allows reading of the signal in dBm. And a turn to HZ allows frequency measurement to 20 kHz in the VF range or 200 kHz in the DSL range. The lightweight unit also allows measurement of dc voltage, dc current, and loop resistance.