The Pro-Ject Strobe It provides a highly accurate method for measuring the rotational speed of a turntable's platter. It achieves this by utilizing a stroboscopic pattern, which relies on the effect of a strobe light to create an optical illusion that allows users to visually confirm the speed. The Pro-Ject Strobe It provides a highly accurate method for measuring the rotational speed of a turntable's platter. The Strobe It is designed to be compatible with turntables that operate at both 33 1/3 and 45 RPM speeds. It allows users to check and adjust the speed settings on their turntable to ensure they match the standard speeds for vinyl records. Instructions for Use:Strobe it shows circularly arranged dashes that are assigned to speed and frequency. Please note the ring that matches your desired speed and frequency (60hz inner ring in the US). Put Strobe it on the turntable platter and start the turntable. The tonearm remains in its rest. Align a mains powered light source directly over the turntable with Strobe it rotating. The dashes of the aforementioned ring should now appear still. If they seem to move slightly forward or backward,