USE: 1. This unit contains a built in 4 hour timer which is activated immediately when the unit is switched on. The unit will power off after 4 hours of use. This helps maximize battery longevity. Unit can be turned back on manually to commence a new 4 hour session. Unit can be turned off manually at any time. 2. This unit features an automatic 24 hours timer that will allow the unit to turn on at the same time each day.