A "Panchromatic" stroboelectric tuner

A new stroboelectric tuner for musical instruments is claimed to be simpler to construct and to use than devices so far described. A single strobo disk rotates at a very constant speed. It is marked out in 12 concentric tracks, each representing a semitone of the musical scale. Each track is divided up into a number of equal divisions such that the ratios of the number of divisions from track to track are almost equal to the ratios of frequencies of successive semitones of the equal tempered scale. The rotating disk is illuminated by a pulse-fed neon lamp. The incoming sound wave is amplified, passes through a zero crossing detector, is then differentiated; the resulting pulses are amplified and fed the neon lamps via a step-up transformer. The lamp thus emits short-duration flashes at the fundamental frequency of the incoming sound wave. When this frequency is any submultiple of one of the track frequencies, the divisions in that track appear stationary. Due to the pulsed illumination these divisions appear perfectly crisp at all frequencies. Sharp or flat misintonation causes the divisions to appear to move clockwise or anticlockwise. No switching or other manual action is required when moving from semitone to semitone, nor from octave to octave. A maximum error of less than 1 cent can be achieved.