The beacons with which I am familiar work on a radio frequency and are on a lanyard around your neck. When you begin your trip, they are turned on and they continually transmit. After the avalanche, the survivors and/or rescuers turn theirs to receive and systematically comb the area to determine where to dig to recover your body, the usual result.

I used one once, wearing it night and day for three weeks. I never had to use it, thankfully.