'Intellisense' technology allows unit to detect welds less than 5 amps. Four redundant sensors in a staggered design eliminate blocked sensors. Unit has auto shut-off after 60 minutes in torch and grind modes.Weld mode has a 20 min. auto shut-off. Versati le cartridge fits in most 4" x 5" vertical windows. Replaceable lithium batteries. 'Smart View' LCD for fingertip control information. Low battery indicator. '3N1' technology allows three modes of operation:weld (shades 9-13), grind (3), or torch (5). Sta ndard size outer cover plate. Soft touch control panel eliminates contaminants and protects from the outside environment. 9 square inches of viewing area and four sensors.