Baby monitors are an extra set of ears--and, in some cases, eyes--that allow you to keep tabs on your sleeping baby.

There are two basic types of baby monitors: audio and video/audio. Both operate within a selected radio frequency band to send sound from the baby's room to a receiver. Each monitor consists of a transmitter (child unit) and one or more receivers (parent units). Video/audio monitors have a small wall-mounted or tabletop camera to transmit images to a video monitor.

A baby monitor's challenge is to transmit recognizable sound (and/or images) over a distance with minimal interference--static, buzzing, or irritating noise--from other electronic products and transmitters, including cordless phones that share the same frequency bands, cellular phones, appliances, and even fluorescent lights. Interference can also be hearing someone else's conversation, which makes it difficult, if not impossible, to decipher the sounds coming from your monitor. Interference can also mean fuzzy reception in video monitors. Overall, interference is probably the biggest complaint parents have about baby monitors.

SHOPPING SECRETS

Feel free to skip this purchase. Some parents are reassured by the constant surveillance of a baby's every whimper and movement. Others find it nerve-racking and feel like they have to be hypervigilant. Decide which category you're in before you go shopping. A monitor isn't a must-have. If you live in a small house or apartment or want a break when your baby is sleeping--which is legitimate--it's OK not to have one.

Consider your home and lifestyle. You may appreciate a monitor with both sound and lights, so you can "see" your baby's cries. The louder he cries, the more lights light up. If you'll be taking business calls during naptime, for example, it can be helpful to turn the sound down low and rely on the lights. A video monitor can serve the same purpose, though we believe an audio monitor with lights can suffice. Similarly, if you live in a large house, you may want a monitor with two receivers rather than just one. In general, look for monitors with features that make it easy to move about, such as a compact parent unit that clips onto your belt. Try it on before buying, if possible; antennas have been known to poke the wearer.

Factor in your phone. To minimize the possibility of interference, choose a baby monitor that operates on a different frequency band from other wireless products in your home. A 2.4GHz cordless phone and a 2.4GHz monitor can interfere with each other. The 2.4GHz frequency band is widely used for cordless phones.

Consider digital if you have nearby neighbors with babies. If you want to be sure the sounds transmitted by your monitor are heard only by you and not by neighbors who might have a similar model (or a cordless phone using the same frequency band), go with a digital monitor, not an analog one. This will also ensure that the sounds you hear are coming from your baby and not the neighbor's. Analog monitors operate on a particular frequency band, much like a radio, sending signals from monitor to receiver in a straight shot. Digital monitors, on the other hand, encode the signal as it travels between the monitor and the receiver, making it nearly impossible for the sounds to be heard by others, and reduces the possibility of running into interference from other electronic devices.

Learn the return policy. Before you buy or register for any wireless product, such as a baby monitor, be sure the store will let you return or exchange it, in case you can't get rid of interference problems. If you receive a monitor as a baby shower gift and know where it was purchased, try it before the retailer's return period (usually 30 days) runs out.

WHAT'S AVAILABLE

The major brands of baby monitors, in alphabetical order, are: Evenflo, Fisher-Price, Graco, Mobicam, Philips, Safety 1st, Sony, Summer Infant, The First Years, and Unisar Bebe Sounds. Prices range from $15 to $200 for audio monitors, $100 to $200 for audio/video monitors. The higher the price, the more features and frills.

IMPORTANT FEATURES

Frequency band. As we mentioned, the closer your monitor's frequency is to that of another device, such as a cordless phone, the more likely you'll hear static or cross talk. One manufacturer, Philips Electronics, has addressed the interference issue by using a new frequency band: 1.9GHz. The new frequency, reserved exclusively for voice-only applications by the Federal Communications Commission, is called DECT technology, for digitally enhanced cordless telecommunications. The Philips SCD 589 baby monitor is the only one we know of that uses the 1.9GHz frequency band. And as far as we know, there's only one cordless phone that uses the 1.9GHz band, also made by Philips. In our tests, the Philips monitors and its brandmate cordless phone, didn't interfere with each other. Overall, the 1.9GHz frequency band is lightly used, at least for now, and can improve your chances of privacy and no interference.

Multiple channels. Some monitors offer only two channels; others, as many as 60. Multiple channels can be an advantage. If you're getting interference, you can change channels and try to get rid of it. Some models use an "auto-select" feature to automatically find a free and secure channel, which is handy.

Sound lights. With this common feature, a monitor's lights turn on when the baby makes a sound; the louder he cries, the more lights light up. Consider this a must-have. It's helpful in a noisy room, plus it lets you turn the volume down and still know when your baby is crying. Some new models have a "vibrate" feature, similar to that found on cell phones or pagers, to quietly alert you that your baby is awake or crying.

Out-of-range indicator. This common feature is a light or beep that lets you know you've reached the range limit of the monitor. Models that lack this feature may let you know you're out of range with static, but that's not as definitive as an out-of-range indictor.

Low-battery indicator. Look for a monitor with a light or an icon on an LCD display that lets you know the batteries in your parent unit are running low.

Extra parent unit. If you have two parent units, you can keep one receiver near your bed and carry the other around with you during the day, or both you and your spouse can listen for your baby at the same time.

NICE BUT NOT NECESSARY

Walkie-talkie. You'll find this feature in models with more than one parent unit. It lets you talk to each other via the receivers.

Talking remotely to your baby. At least one monitor we tested, the Philips SCD 589 baby monitor, has an "intercom" that allows you to speak to your child in his crib by pushing a button on your parent unit.

Auto playback or music. Some baby monitors, such as the Sony BabyCall, let you record a voice message for your baby or play lullabies or other soothing music.

Expandability. Some monitors let you add more cameras, a VCR, or webcam so the system covers more areas in your house. Other models have additional parent units you can buy.

DEFINITELY NOT NECESSARY

Attaching the monitor to your baby's crib. All of the monitors we tested could easily detect baby's sounds from 5 or more feet away, so there's no need to put the monitor directly on the crib rail.

WORKS BETTER IN THEORY

Pager or parent-unit finder. If you've lost the parent unit, you can press a button on the child unit to make the parent unit beep. Unfortunately, the parent unit must be turned on for this feature to work, and if you leave the parent unit on, the batteries may go dead before you find it.

RECOMMENDATIONS

Among the models we tested, the digital baby monitors are top-rated. Short of DECT technology, there's no guarantee against interference with either digital or analog monitors, although digital monitors are less susceptible and more private. One digital model in particular, the Philips SCD 589, is loaded with features, and since it operates in the fairly lightly used, for now, 1.9GHZ frequency band, it's unlikely to pick up interference. However, at $200, it's pricey. See our full report on this model, available to ConsumerReports.org subscribers.

If you anticipate interference and want to spend less than $200, buy a less-pricey digital model that's not in the same frequency band as other wireless products in your home, and consider models with more than two channels. The other digital monitors we tested were very good: The Graco iMonitor ($90) has two parent units; a similar version with one parent unit is available for $60. The Summer Infant Secure Sounds ($50) is a good choice for privacy, though, like the Graco iMonitor, it has fewer frills than the Philips SCD 589. See our full Ratings, available to ConsumerReports.org subscribers for details.

We suggest avoiding the Evenflo WhisperConnect Sensa ($50). It has a Pet Sensor, which is designed to alert you to any unusual movement around your baby's crib--a cat or other pet climbed in, say. That feature worked well, but you can easily keep pets away from the crib by closing the door to your baby's room. In addition, we found that one of the three samples we tested had an annoying problem: The "out of range" alarm would go off at random. This happened over and over again with that particular sample, and once or twice with one of the other two samples we tested.

The audio/video monitors we tested have small color screens, and unlike earlier models, reasonably good pictures. However, we found them to be susceptible to interference, particularly from microwave ovens in use. Some models, such as the MobiCam ($190), let you tape to a VCR or watch your monitor on the television set. But overall, we don't see much need for a video baby monitor.

Copyright © 2003-2007 Consumers Union of U.S., Inc.

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