Strong anti-interference Low power consumption Idea for home, office, factories, guest rooms in hotel etc.. Installation Open the battery compartment cover of the receiver load 4 x R14/C batteries (Not included) Fix the transmitter on the wall near the door with screws or adhesive tapes. Avoid placing transmitter near high temperature moist area, metal or electromagnetic surfaces Please replace the battery if the transmitter is not functioning properly Package Dimensions10.5x5x17cm