Lou at wildsnow.com has an essential post on how various electronic devices interfere with avalanche beacons. The quick hit on this is that several commonly carried PED's, such as cell phones and Ipods, can render your beacon useless in search mode. Since this information is both critically important and horribly out of season, I'll try to link back again once winter arrives. In case I forget, make sure you read—and remember—Lou & Jonathan's article.
Andy Lewicky is the author and creator of SierraDescents