Abstract: A glass container inspection machine includes a head assembly, a console, and a cable connecting the two. The head assembly includes a measuring oscillator and a reference oscillator the outputs of which are applied to a Phase Detector Multiplier. A fixed resistance in the output circuit of the measuring oscillator is selected so that the output of the Phase Detector Multiplier is the same no matter what the frequency of the oscillation. The oscillation and the Phase Detector Multiplier are part of a Phase Locked Loop, the amplifier portions of which are in the console. The machine is comprised of four such data channels, each of which includes a head assembly operating at a different oscillator frequency. All components that are frequency dependent are included in the head assembly while all components in the console are frequency independent. Thus the output of any of the head assemblies may be connected via the cable to any of the data channels of the console.