1. 4 modes: sound only, flash only, sound and flash, sound and light on. A light on can turn on at night
 2. Memory function: After turning off the power, remember the music previously set. No need to set music again
 3. Self-operating doorbell that does not require a battery, do not worry if the battery has power, so do not miss important visitors
 This button uses kinetic energy. No battery needed
 4. Amazing lights, strong ringtones. Especially suitable for the elderly, pregnant women, housewives.