Shielding Flaw Detection and Measurement in Quadrature Amplitude Modulated Cable Telecommunications Environment

A marker signal source comprising a source of at least two unique signals,

• a control arrangement to control each of said at least two unique signals in frequency and amplitude to avoid interfering with coexisting payload signals being distributed by a broadband communication system to form controlled unique signals, and
• a signal combiner to combine said controlled unique signals with said coexisting payload signals.

The marker signal source as recited in claim 27, wherein said at least two unique signals are a double side band, suppressed carrier signal.

A marker signal receiver comprising

• a filter or tuner tuned to a center frequency of a marker signal, said marker signal including at least two unique signals,
• a spectrum analyzer for determining spectral content of an output of said filter or tuner, and
• a comparator for comparing a spectrum of an output of said spectrum analyzer with a spectral content of said marker signal.