A typical baby monitor, also known as a baby alarm, is a simplex (uni-irectional) 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).