The compatible with Sharp AccuSet Alarm Clock with Display Dimmer is pre-programmed with the time so there is no need to worry about setting buttons. Just select your time zone at the bottom of the clock and turn on the DST if applicable. Plug the clock into an approved electrical source. For quick adjustment for Daylight Savings Time, slide the DST switch at the bottom of the clock to ON to add and hour (+1 hr. ). For Standard Time slide switch to OFF to subtract an hour (-1 hr. ). The compatible with Sharp AccuSet is also equipped with a High/Low Dimmer control giving you the ability to adjust the display brightness to your liking. The backup battery is a button cell battery CR2032. It is pre-installed and used for backup of the time settings if the power is interrupted. It is in a screw-secured cabinet at the bottom of the clock. This battery will last for several years. Automatically Sets Time High Low Dinner Control . 9 inch White LED display CR2032 battery is pre-installed and is used for the backup battery Product dimensions (5. 5” x 2. 45” x 2. 6”) / Package dimensions (5. 75 x 3. 5 x 2. 75 inches)