At some stage in gramophone restoration it will be necessary to calibrate the speed of the turntable so that with the indicator plate showing 78 rpm it is known that the turntable is actually turning at this speed. Manufacturers differ in the way adjustments are made but no matter what system of adjustment is used, common to all is the necessity to be able to assess the actual speed of the turntable. This is either done with a strobe disc or using a digital tachometer. This video explains in more detail the two methods. For more information please visit my website at www.restore-a-gram.co.uk