A typical baby monitor, sometimes also known as a baby alarm, is a simplex (uni-directional) radio 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, and some have a feature allowing music to be played on the transmitter (and thus played to the child). A human infant The word infant derives from the Latin word in-fans, meaning unable to speak. It is commonly used as a slightly more formal word for baby (the youngest category of child). ... Inside a condenser microphone. ... Closeup of a loudspeaker driver A loudspeaker, or simply speaker, is an electromechanical transducer which converts an electrical signal into sound. ... A transceiver is a device that has a transmitter and a receiver which are combined. ...

One of the primary uses of baby monitors is when the infant is asleep in a separate room, allowing caregivers to keep track of any problems while away from the baby.

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 modern baby monitors also incorporate a digital camera to show video footage on the receiver in a similar method to web cams, and some others allow the receiver to be plugged into a television. Some devices also incorporate movement sensors on the transmitter 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. A SiPix digital camera next to a matchbox to show scale. ... A web camera (or webcam) is a real time camera whose images can be accessed using the World Wide Web, instant messaging, or a PC video calling application. ... A vibrating alert is on communications devices to notify the user of an incoming connection. ...

It is common for the receiver to use batteries as their source of power allowing it to go with the caregiver. The transmitter stays with the infant crib and is usually plugged into a socket. Some baby monitor packages include two receivers. Four double-A (AA) rechargeable batteries In science and technology, a battery is a device that stores energy and makes it available in an electrical form. ... CEE 7/7 plug and socket Domestic AC power plugs and sockets allow a connection between the mains electricity (household, usually single-phase, AC electrical power) and the appliances commonly used in homes. ...

The frequency used by the devices usually lies in the range of 49–50 megahertz, though some models can go as high as 900 MHz. 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. Sine waves of various frequencies; the lower waves have higher frequencies than those above. ... MegaHertz (MHz) is the name given to one million (106) Hertz, a measure of frequency. ...

There have in the past been baby monitors that used a length of cable (around 100m) instead of radio or, alternatively, using mains wiring.

References

• Baby monitors - information for deaf and hard of hearing people (factsheet)
• Baby monitors - information for deaf and hard of hearing people at the RNID, retrieved 14 January 2005

The Royal National Institute for Deaf People, which prefers to be referred to as RNID, seeks to represent all deaf and hard of hearing people in the UK. RNIDs headquarters are in Islington, in Central London (19-23 Featherstone Street, LONDON EC1Y 8SL). ... January 14 is the 14th day of the year in the Gregorian calendar. ... 2005 (MMV) was a common year starting on Saturday of the Gregorian calendar. ...

External links

• Baby monitors at BabyCenter.com
• Baby Monitors @ Baby-Monitors.org