The AC403 is the updated version of the much loved AC401.
It has updated software inside and a sleeker all white appearance.
Both of these monitors have 8 channels so should you experience any interference as is possible with any analogue/wireless product you have another 7 channels that you can select to reduce the interference.
As a result of the 8 channels you can use more than one AC401/AC403 or one of each model in the same home.
If you use more than one AC401 or AC403 we would also advise that you sticker each set with a different colour or baby name, this will prevent any mix ups or queries should one monitor beep for any reason.
Please see below the Angelcare Product Comparison Chart document that lists each feature per model for all Angelcare Monitors.