Technology marches on -- bringing us wonderful new household appliances like space-age microwave ovens with radio waves that penetrate food. They jiggle molecules around, causing heat inside that cooks food without external heat or flame. It's great stuff that we soon get used to -- and begin taking for granted. Microwaves were introduced in the early '70s and today many are 15-, 20- or even 25 years old. They're often still being used on a daily basis. As your microwave oven ages, remember two words: "efficiency" and "safety." First, make sure it still delivers full power for proper cooking. One cup of water should boil within 3 minutes. If not, have it checked. A dirty interior also can cut efficiency. Strange noises, electric arcing and a flashing display say it's time for a check-up. If your unit is more than 15 years old, have it tested for radiation leaks by a professional technician -- unless you want that nice red sunburned look when you cook. And that's the On The House tip for today.