There are two basic types of baby monitors: audio and video. Audio monitors work within a selected radio frequency band to send sound from the baby’s room to the receiver. Video monitors use a small camera mounted on the wall or on a table that transmits images to a monitor similar to a television.

Yet another way to monitor your baby is with motion sensors, pads under the mattress that alert you when their movement has stopped completely for more than 20 seconds. While some parents may find motion sensors reassuring, keep in mind that they are not medical devices and should not be used in place of prescription heart or respiratory monitors to detect conditions such as sleep apnea. You also shouldn’t rely on them to prevent sudden infant death syndrome, the cause of which is still unknown.

WHAT IS AVAILABLE

Major brands are BebeSounds/Unisar, Evenflo, First Years, Fisher-Price, Graco, Safety 1st, and SBC/Phillips.

Price range: The baby monitors we tested ranged in price from $20 to $50 for audio monitors, up to $150 for audio/video monitors, and around $100 for motion sensors.

IMPORTANT FEATURES

The challenge with a baby monitor is transmitting recognizable sound from a distance with minimal interference from other wireless devices. Here are some additional features to consider when shopping for a monitor:

Compact parent unit. The smallest parent units are about the size of a large wallet. You can use the integral belt clip to free up your hands, but the antenna can poke you.

Additional parent unit. This unit can stay, for example, in her bedroom while the other is carried around the house.

Battery for the infant unit. All of the kids’ units we tested can be plugged into the wall for power, but four can also use AAA or AA 9-volt alkaline batteries (not included). All parent units have this option. The battery option is useful in the event of a power outage and also allows you to take the unit where there are no electrical outlets, such as outdoors.

Rechargeable batteries included. This money saving feature is provided with the parent unit on some models. You can buy alkaline or rechargeable batteries for the other parent units.

Low battery indicator. A light or tone warns of the need to recharge or change the batteries in the parent unit. Some models also have indicators for the child unit.

The following features are nice but not necessary:

Intercom. Pressing a button and speaking to the parent unit lets you reassure your baby that she’s on the way.

Video monitor. The Summer Infant monitor we tested has a video monitor, but its so-so image quality limits its usefulness.

This function works best in theory:

Search function. A model from The First Years promises to help you find a missing parent unit. Press a button on the child unit to make the parent unit beep. Unfortunately, it doesn’t work if the missing drive has been powered off.

HOW TO CHOOSE

Performance differences. More money gives you more extras, not necessarily more security for your child.

Recommendations Try an audio baby monitor at the store to see how it fits in your hand and how it feels when you clip it on. Video monitors are still quite expensive. If you buy one, you may find that an audio monitor is all you really need. Also use the following tips and the Consumer Reports ratings, available to ConsumerReports.org subscribers, to help you choose the best monitor for your needs.

Decide how much you want to monitor. The latest generation of baby monitors claims to allow constant monitoring of your baby’s every moan, breath and movement. For some parents, that’s reassuring. For others, such non-stop monitoring is stressful. So keep in mind that a monitor is not a must. If you live in a small house or apartment or feel that you would like to rest when your baby is sleeping, which is legitimate, it is okay to choose not to have a monitor.

Consider your home and lifestyle. In many situations, you may appreciate a monitor with sounds and lights so you can also “see” your baby’s cry. If you’re going to be taking business calls during nap time, you might want to be able to turn the volume down very low and rely on the lights. A video monitor can also serve the same purpose, but it is very expensive and not very portable. Similarly, if you have a large home, you may want a monitor with two receivers instead of just one, but it may also be convenient in a small home. And in general, look for monitors with features that make them easy to move around, like a compact parent unit that clips onto your belt. (Try it before you buy, if possible; we found that the antennas tend to poke the user.)

Choose between audio or audio/video. A good audio monitor will let you know if your baby is awake or asleep, moving or not. Our tests showed only so-so image quality from the Consumer Reports-rated video monitor. You can tell that your baby’s eyes are open, for example, but you can’t make out many details.

Be careful with the frequency. None of the baby monitors tested by Consumer Reports were immune to static. The closer your monitor’s frequency is to that of another device, the more likely you are to hear static or interference. You can reduce interference if your monitor allows you to switch to a different channel within its frequency band, as all models tested by Consumer Reports do.

Consider your phone. Choose a monitor that operates on a different frequency band than your wireless phone. Most newer cordless phones are 2.4 gigahertz or 900 megahertz. If you have a 900 MHz cordless phone and a 900 MHz monitor, they may interfere with each other.

Check the range. All models tested by Consumer Reports that claimed signal distance range met or exceeded it in our outdoor test. Choose a model with a suitable signal range for your home. However, some home construction materials, such as concrete and metal, can reduce the range.

Know the return policy. Since you often can’t try monitors before you buy them (monitor models are usually not available, and conditions in the store can be very different from those in your home), be aware of the return policy of the store or the website where it is you are buying or registering. You’ll want to be able to get a monitor back if you’re not happy with it for whatever reason. (Common problems include static and interference from cordless phones or answering machines, even ambient sounds from an air conditioner or a neighbor’s dog barking.)

Certificate. Although they are listed as electrical products under Underwriters Laboratories, there is no specific certification program for these products. Of course, as equipment that generates, uses, and can radiate radio frequency energy, baby monitors must comply with Part 15 of the FCC rules within the USA. That means the device may not cause harmful interference and You must accept any interference received, including interference that may cause undesired operation. A few models, numbering around a million units, were recalled in the late 1990s and again in 2003. Problems included faulty wiring that could present a smoke and fire hazard, as well as batteries that can rupture and irritate the skin.

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