The baby monitor consists of a transmitter (called the child's station) and the receiver (the parent station). Her action (in its simplest version) involves the transmission of sounds (crying, cooing) using a microphone from the station to the station a parent of the child.
Are commercially available baby monitors, which consist only of a transmitter and a receiver is your phone. Such a device has in its offer firm Reer: programming the number you have to call the nanny, the baby starts to cry.