The Angelcare movement sensor with sound monitor lets you stay connected and aware of your babys every movement, even when you"re in a different room. The set includes a nursery sound monitor, sensor pad and 2 parent units. With 2.4 GHz frequency band, this baby sound monitor wirelessly transmits error-free audio signals. The under-the-mattress sensor pad easily detects all your baby"s movements. The nursery unit alerts you with an alarm sound if no movement is detected for 20 seconds. It has an optional Tic sound feature to let you know that the sensor pad is working. The unit has 2 channels to choose from for maximum reception and reduced interference. This wireless movement sensor"s nursery unit automatically starts operating in battery mode in case of a power failure. Its low battery indicator alerts you when the charge is low. This baby monitor unit comes with all necessary accessories such as an AC Adapter and an instruction manual.