From the Manufacturer
The AC401 deluxe plus version will detect baby's slightest movements, even while she sleeps, and sound an alarm if no movement whatsoever is detected for 20 seconds. The angelcare sensor pads with sound monitor has many added features. The nursery unit has a soft nightlight and room thermometer. The temperature is displayed on the parent's units, which can alert you when the temperature falls out of your preset range. Additional features include an out-of-range indicator, a parent's unit locator, optional voice activation and a color LCD on each parent's unit which displays all the data. Both parent's unit comes with 4 AAA rechargeable batteries and a charging base. This monitor continues to offer an optional tic feature. If movement is detected, they will tick. Additional features include sound lights and movement indicator lights. This model operates on both 927 MHz and 2.4 GHz frequencies. The sound monitor operates on the 927 MHz frequency so there is no interference from 2.4 GHz equipment. The monitor has 8 channels and an 820' range.