battery power, LED array
STROBOSCOPE
Model : DT-2199
* Stroboscope uses high intensity LED array.
* LCD display with backlight.
* Stroboscope range : 100 to 99,999 RPM.
* Power supply : Batteries, 1.5 V ( UM-1, D ) x 4 PCs.
* AC/DC adapter is optional.