An apparatus for detecting spectral components in a predetermined frequency band within a signal includes first and second processing devices and first, second, and third connectors tuned to the frequency band. The first processing device includes first, second, and third elements. The second processing device includes fourth, fifth, and sixth elements. The first connector is coupled to the first and fourth elements, the second connector to the second and fifth elements, and the third connector to the third and sixth elements. An apparatus for analyzing spectral components in predetermined frequency bands within a signal includes an input for receiving the signal, a device for isolating a portion of the signal, and frequency detectors coupled in parallel to the device. Each frequency detector corresponds to a frequency band and generates an output signal component corresponding to a proportion of energy of the spectral components detected by the frequency detector.