Special Features: 1. The graceful and delicate design will give you the visual enjoy from line to colour. 2. The working distance is more than 150m which makes sure to meet the requirement of all kinds of family houses and high buildings. 3. More than 10 thousand sets of non-repeated coding/decoding available to ensure free from interference 4. Different sound options. * Soft ding dong sound * Loud ding dong sound * Popular songs * Soft music * Twelve songs * Required by customers