Only single alarm available. 8 minutes later the alarm will ring again. Simple as that. The backup battery (cell button battery CR2032 ) already installed, which normally will last 2 years of life.
I would recommend to anyone who is tired of not having your clock keep time after a power outage. It's amazing that it sets the time automatically. I'm still not 100% sure how it does it, but it does. Has a nice 6-level plus AUTO dimmer level that won't light up the room unless you want it. Highly recommended!