This app prevents missed call by playing ringtone with maximum volume in seconds you set.It works when your ringer mode is sound. (not vibration and silence)You can mute ringtone by upside (screen) down.You have to change direction of screen to ‘Upside down’ again if your device is state on ‘upside down’ when you get a call.Ads may be displayed when It becomes Max Volume or mute by this app in free version.