What is the primary function of a foreign voltage detector (FVD)?

The primary function of a foreign voltage detector (FVD) is to test voltage levels on cables. This device is specifically designed to identify the presence of foreign voltages that may be affecting the performance of telecommunications equipment. It helps technicians ensure that the electrical conditions of the cables are safe and within expected parameters before proceeding with maintenance or repairs.

Measuring signal strength focuses on the strength of communication signals rather than electrical voltage levels in cables, which is outside the FVD's primary function. Evaluating resistance in circuits involves assessing how much a component resists the flow of current, which is a different measurement not typically associated with the capabilities of an FVD. Analyzing signal distortion pertains to assessing the integrity of the transmitted signals, including any alterations caused by interference, rather than measuring voltage directly.