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A typical baby monitor, also known as a baby alarm, is a simplex (uni-directional) transmitter and receiver system used to remotely listen for noises made by an infant. The transmitter, equipped with a microphone, is placed near to the child and the receiver equipped with a speaker, is carried by, or near to, the person caring for them at the time. Some baby monitors are duplex (bi-directional), using transceivers that allow the caregiver to communicate back to the baby (parent talk-back), and some have a feature allowing music to be played on the transmitter (and thus played to the child).
One of the primary uses of baby monitors is when the infant is asleep in a separate room or floor, allowing caregivers or parents to keep track of any problems while away from the baby.
For those worried about Sudden Infant Death, a monitor should only be used under the supervision of a paediatrician or other doctor. Although commonly used, there is no evidence that these monitors prevent SIDS, and many doctors believe they provide a false sense of security[1].
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Video baby monitors: baby cams
Some modern baby monitors also incorporate a video camera to show pictures on the receiver using radio waves in the unlicensed 2.4 GHz band, either by plugging the receiver into a television or by including a portable LCD screen; they are often called baby cams.
Some baby cams can work with low minimum light level (night mode). Most video baby monitor today has night vision feature. This advance technology that previously used only by the military, is essential for night time viewing. Infrared LEDs attached on the front side of its camera allow you to see your baby in the darkened room. When the light get dim, video baby monitor that has night vision mode, will switch to this mode automatically.
Wired and wireless
Baby monitor generally uses wireless systems, but can also use corded ones (i.e. cable or X10).
Audio wireless systems, using DECT, are completely interference free and have a range up to 300 m [2]
Video wireless systems:
- Suffer from interferences with WiFi ( 2.4GHz) or TV signals.
- Have shorter range than audio or X10 monitors.
A mix system offers a cord connection, using the home grid, and a wireless one from the outlet to the receiver.
Other features and technologies
- Baby monitors may incorporate a visible signal as well as repeating the sound. This is often in the form of a set of lights to indicate the noise level, allowing the device to be used when it is inappropriate or impractical for the receiver to play the sound.
- Some devices also incorporate movement sensors on the transmitter (commonly in the form of a pressure-sensitive mat placed beneath the child's mattress) allowing it to warn caregivers of possible sudden infant death syndrome. Other monitors have a vibrating alert on the receiver making it particularly useful for people with hearing difficulties.
- It is common for the receiver to be small and portable and to use batteries as their source of power allowing it to go with the caregiver, around the house. The transmitter stays with the infant crib and is usually plugged into a socket. Some baby monitor packages include two receivers.
- The frequency used by the wireless audio devices usually lies in the range of 49–50 megahertz, though some models can go as high as 5.8 GHz. As with all wireless transmission systems there is the possibility that a receiver used by a third party could pick up the transmissions. To aid this many models allow a choice of bands. Models using DECT avoid this problem, though concerns have been raised over the level of microwave radiation generated by such systems.
- There have in the past been baby monitors that used a length of cable (around 100 m) instead of wireless systems.
- There have in the past been baby monitors that used existing domestic wiring to carry their signal, ie. by plugging both transmitter and receiver into the same circuit.