The angelcare AC420 sound monitor is the sound only version of the angelcare AC401 movement and sound monitor. It offers the same technology as its bigger sister, but does not include the sensor pad. Combining 2 frequencies and 8 channels, it provides optimal sound quality and minimises interference. The parent unit is portable and rechargeable and has a full colour digital LCD screen that clearly shows all the available functions as well as the temperature in babya€™s room. The reach is 100 meters indoors and 250 outdoors. The baby unit has a night light in the shape of a halo. The sound transmission of this monitor can be can be continuous or sound activated. Other features include various alarm indicators like out of reach and battery low. 4x AAA rechargeable batteries are included for the parents unit, while 4x AAA standard batteries (not included) can be inserted in the nursery unit so it will automatically revert to battery power in the case of a power failure