A clear, loud beep indicates radio waves stronger than the level you select. If you move closer to the radio source, the beep becomes more frequent, and will ultimately become a solid tone if you move closer still. Or, if you move away from the source, the beeping will stop. Minimum sensitivity is .001 milliwatt per cm2, making it much more sensitive than the radio/microwave section of the TriField® Meter. At the highest sensitivity, it will detect a typical cellular phone tower within 300 feet line-of-site, a typical analog cell phone 40 feet away, a digital phone 20 feet away, and a microwave oven (in use) 10-50 feet away. However, you will usually use a less sensitive setting. It's most sensitive from 100 MHz - 3 GHz, so ordinary cordless phones do not cause much interference (detectable at about 2 feet). The switch on top lets you select standard sensitivity, high sensitivity or "off". In addition, a control on the side can raise or lower the overall sensitivity. The unit chirps once each time you turn it on to indicate that the battery is good. With the sensitivity on "high", you'll be surprised at the places (and times) you find radio/microwaves.The unit comes with a 3-volt lithium coin battery, which has a typical life of 3 years (assuming it "beeps" with a typical 10% duty cycle for 10 minutes a day) or a 6-year life if it very rarely beeps. The replacement battery (Lithium type 2032) is available at most drug stores.

The MicroAlert comes with a one-year warranty, replaceable battery and a pocket clip. It's made by AlphaLab, Inc. in Salt Lake City. This unique device will fill you in on a lot of things you'd have never guessed (like strong radio waves on some wall outlets but not others in the same building). It's also great for restaurants when somebody at the next table uses a cell phone. If the MicroAlert is turned "on", it will, without you having to say a word, remind the caller that he is "violating" your air space.