The Angelcare AC 201 is the base model baby monitor that features both sound and movement monitors. The sensor pad which is placed under the cribs mattress and is able to detect even the slightest baby movement, such as breathing, that typical baby monitors will not catch. There is adjustable sensitivity and an alarm will sound after 20 seconds of no movement and an optional "tic" can be played to hear the baby's movements. The sensor pad is attached to an external sound monitor which picks up any sounds made by the baby in the nursery. All sounds and movements are transmitted to the parent monitor, with the option of choosing one of two channels to minimize interference. Lights and a speaker on the parent unit allow you to "see" and hear baby sounds. The parent unit operates on rechargeable NiCad batteries, while the nusery unit runs with an AC adaptor and 4 AAA batteries as backup.