CRBT is a sound effect that the calling user hears when the mobile phone is called. China Unicom calls this service ringback tone, which belongs to personalized ringback tone service. It is a service customized by the called user, which provides a pleasant music or greeting for the calling user to replace the ordinary ring back tone. That is, when the called user starts the service, if other users call the user, the calling user will hear the personalized ringback tone set by the called user in the system instead of the monotonous "beep, beep" ringback tone.
Ringtones generally refer to your personal ringtones, such as setting ringtones for incoming calls. When other users call you, the ringtone you set will ring automatically. There are usually three kinds of ringtones: real ringtones, special effects ringtones and funny ringtones. The formats are MP3, waw, mmf, midi, etc. With the support of mobile phone manufacturers, different types of contacts can set different ringtones for them to distinguish. Due to the popularity of mobile phones, the formats of ringtones are diversified.
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