A baby monitor, also known as a baby alarm, is a radio system
used to remotely listen to sounds made by an infant. An audio monitor consists
of a transmitter unit, equipped with a microphone, placed near to the child. It
transmits the sounds by radio waves to a receiver unit with a speaker carried
by, or near to, the person caring for the infant. Some baby monitors provide two-way
communication which allows the caregiver to speak back to the baby (parent
talk-back). Some allow music to be played to the child. A monitor with a video
camera and receiver is often called a baby cam.
One of the primary uses of baby monitors is to allow attendants to hear when
an infant wakes, while out of immediate hearing distance of the infant.
Although commonly used, there is no evidence that these monitors prevent SIDS,
and many doctors believe they provide a false sense of security. Infants and
young children can often be heard over a baby monitor in crib talk, in which
they talk to themselves. This is a normal part of practicing their language
skills.
Some baby monitors also use a video
camera to show pictures on the receiver, either by plugging the receiver into a
television
or by including a portable LCD screen. This type of surveillance camera is often called a baby
cam.
Some baby cams can work at night
with low light levels. Most video baby monitors today have a night vision
feature. Infrared
LEDs attached on the front of the camera
allow a user to see the baby in a dark room. Video baby monitors that have
night vision mode will switch to this mode automatically in the dark.
Baby monitors continue to evolve and
now also can utilize features such as night lights and built-in lullabies.
These are not available in all monitors.
Movement monitors
A baby movement monitor uses sensor pads placed under the crib mattress to
detect movement, if movement stops for more than 20 seconds an alarm will sound.
Wired and wireless
Baby monitor generally use wireless systems, but can also use wires or may
operate over existing household wiring such as X10.
Wireless systems use radio frequencies that are designated by governments
for unlicensed use. For example, in North America frequencies near 49 MHz, 902
MHz or 2.4 GHz are available. While these frequencies are not assigned to
powerful television or radio broadcasting transmitters, interference from other
wireless devices such as cordless telephones, wireless toys, computer wireless
networks, RADAR, Smart Power Meters and microwave ovens is possible.
Digital audio wireless systems using DECT, are resistant to interference and
have a range up to 300 m.
Analog audio transmissions can be picked up at a distance from the home by a
scanner receiver or other baby monitor receivers, and so present a risk to
privacy as long as the transmitter is switched on. Digital transmission such as
Frequency-hopping spread spectrum provides a level of protection from casual
interception.
Some wireless baby monitors support multiple cameras on one handheld monitor-receiver.
These systems are even compatible with a standard wireless security camera.
