Abstract: A method for locating faults or failures in R-F coaxial cable TV transmission facilities is shown and described. A fault locator signal frequency is inserted into a cable system, and low magnitude signals are emitted by means of a band pass filter and radiating element. The radiated R-F is detected to determine coaxial cable system operation. Band pass filters and radiating elements are located at each point to be tested.An apparatus for emitting a controlled narrow band of R-F energy which utilizes a band pass filter and a radiating element is also shown and described.This is the disclosure of intentional, controlled, discriminate R-F radiation used for fault detection and a coupler-band pass filter to accomplish it.