1, 35 songs selectable 2, Volume control 3, Range more than 100 meters 2 4, SMT NEW TECHNOLOGY 5, ... selection.5) Easy instillation, no wiring needed, no labour involved. (wireless doorbell)6) Easy mobility, suitable for house, villa, office, hotel ... , food joints, dormitory, factory etc.7) New innovative technology (SMT), range more than 100 meters8) Four colours for the switchs can ...