Speedometer RPM measurement, strobe speed and motion analysis with the Extech 461825 combined photo tachometer and stroboscope. The unique display reverses the direction of the drawing depending on which measurement mode you are using. The tachometer memory stores the last, max. and min. readings, which can then be recalled. The course and flash rate of the strobe can be fine-tuned in 3 ranges. Includes 4 AA batteries, reflective tape and carrying case.