Simply turn the timer so that the side with the number faces up and the timer starts counting right away. The alarm volume can be adjusted to high, low and off by flicking the switch. Requires 2 AAA batteries to use (Batteries not included). It has 15, 20, 30, 60 minutes sets suitable for many uses such as exercising, studying, cooking and taking a nap. Beside, 1-3-5-10 minutes &25-5-45-15 or custom time all availalbe.