The RT-7690-2 is a self levelling, remote controlled, 2 rotating beam laser for interior and exterior applications. Self Levelling: Place the RT7690-2 on any surface, and the unit's self levelling system levels and plumbs without ever having to move the laser. Out of Level Sensing eliminates costly errors (even on busy jobsites where vibration, impacts and temperature changes are common). The RT-7690-2 has both audio (beeper) and visual (blinking beam) out of level indication that warns the user if the unit has been bumped or disturbed after initial setup. Line Dither/Scan Mode: has six adjustable line lengths allowing the user to select the laser beam length and brightness that meets their specific interior level and plumb application requirements. Spin Mode: has three different speeds letting you select the beam brightness based on the ambient lighting conditions and specific interior or exterior application. Remote Control: The RT-7690-2 has an RF remote control that allows operation of ALL the laser functions anywhere on the jobsite. Remote control allows a single person to operate the laser system. User Recalibration: Unlike other lasers, users can easily calibrate the RT-7690-2, keeping it on the jobsite and saving both time and money.