How to set the ringing sound effect and DND mode of the Xiaomi Smart Doorbell 3S chime?

To set the ringing sound effect, you can navigate to the [Mi Home/Xiaomi Home] APP >> select [Xiaomi Smart Doorbell 3S] >> tap the three-dot icon at the upper right corner >> [Doorbell settings] >> select [Indoor receiver settings] >> [Ringtone] >> you can select [Ding-dong], [Fantasy], [Comic] and [Clarinet] as your preference.
To set the DND mode, you can navigate to the [Mi Home/Xiaomi Home] APP >> select [Xiaomi Smart Doorbell 3S] >> tap the three-dot icon at the upper right corner >> [Doorbell settings] >> select [Indoor receiver settings] >> [DND mode] >> turn on/off the option as you need.