Buzzer in Vacuum

With four toothed wheels each 75 mm dia, fixed 6 mm apart on a shaft, projecting as spindle with slight taper at its end. Wheels have 36, 45, 54, and 72 teeth respectively, used with whirling table

Square section with tapered mouthpiece, made of polished wood, with graduated sliding piston, square in section having a knob at the end for easy handling. The slider is marked with a diatonic scale. It is used to investigate phenomenon of beats in conjunction with a second pipe of same type. Approx. overall length when extended 840mm.