A video baby monitor system has a child unit with a back-up battery, a video camera, a microphone, and a transmitter configured to transmit video signals representing video images sent from the camera and audio signals representing sounds sent from the microphone. A parent unit having a receiver for receiving the video signals and the audio signals, a video screen for displaying the video images, and a speaker for emitting the sounds. The child unit is configured to operate on primary power from an external power source and to operate on back-up power from the back-up battery source. The monitor system is configured to switch from the primary power to the back-up power and to deactivate at least one video function upon detecting a loss of the primary power.