The Type 1535-B Contactor (Figure 1) is a control and coupling device for synchronizing a stroboscope with a rotary shaft so that motion can be observed as a function of shaft angle. It is especially useful in the examination of relatively low - speed machinery, with the Type 1532-D Strobolume, in such applications as the timing of loom shuttles and the adjustment of register in printing. It can be used equally well with the Strobotad® electronic stroboscope or with the combination of Strobotac and Strobolux, at speeds up to 1000 rpm. For higher speeds the Type 1536-A Photoelectric Pickoff should be used.