A baby monitor (English: baby monitor), also known as a baby alarm (English: baby alarm), is a radio system used to remotely listen to sounds made by an infant. The audio projector consists of a transmitting unit, equipped with a microphone, placed near the child. It transmits sounds by radio waves to a receiving unit with a loudspeaker carried by, or near, the person caring for the child. Some baby monitors provide two-way communication that allows parents to talk to the Child (re-talk of the parents). Some allow playing music to the child. The screen with a video camera and a receiver is often called a baby diameter monitor camera.
Some baby monitors use a video diagonal surveillance camera to display images on the receiver, either by connecting the receiver to the TV or by including a portable LCD display. This type of surveillance camera is often called a child diameter surveillance camera. Some children's cameras can work at night with low light levels. Most baby monitors today have a night vision feature. Infrared LED lights located on the front of the camera allow the user to see the child in a dark room. Baby monitors with night vision mode will switch to this mode automatically in the dark. Some high-end baby cameras now work over a Wi-Fi network so that parents can watch children through a smartphone or computer