A sensor system uses positive closed-loop feedback to provide energy waves into a medium. The medium can be coupled to the muscular-skeletal system or be part of the muscular-skeletal system. A sensor comprises one or more transducers, an edge detect circuit or a reflecting surface. A parameter is applied to the medium and the parameter affects the medium. A transducer receives an energy wave that has traversed the medium and generates an energy wave signal. The edge-detect receiver receives the energy wave signal signal from the transducer and generates a pulse upon sensing a leading edge corresponding to a wave front of the energy wave. The edge-detect receiver comprises a preamplifier, a differentiator, a digital pulse circuit, and a deblank circuit. The transit time, phase, or frequency is measured of the propagating energy waves and correlated to the parameter being measured.
