An oscillator circuit and system are provided having a peak detector that can determine a peak voltage value from the oscillator. An elastomeric ring is configured for releasable engagement in the seat on the abutment member, and is retained in a retainer ring which in turn is in swivel engagement with a concave inner surface of a cavity in a cap which is secured in a recess in a dental appliance such as a denture, partial denture, or the like. The first SAW is transduced to a first output electric signal, respectively, at the output interdigital electrodes Rxaj and Rxbj. The planar region contains a number of target points that are to be interpolated from the first color space to the second color space.