The iPhone allows audio conferencing, call holding, call merging, caller ID, and integration with other cellular network features and iPhone functions. For example, if a song is playing while a call is received, it gradually fades out, and fades back when the call has ended. The proximity sensor shuts off the screen and touch-sensitive circuitry when the iPhone is brought close to the face, both to save battery and prevent unintentional touches. The iPhone only supports voice dialing through third party applications and video calling is not supported at all.The iPhone includes a visual voicemail (in some countries) feature allowing users to view a list of current voicemail messages on-screen without having to call into their voicemail. Unlike most other systems, messages can be listened to and deleted in a non-chronological order by choosing any message from an on-screen list. AT&T, O2, T-Mobile Germany, and Orange modified their voicemail infrastructure to accommodate this new feature designed by Apple. A music ringtone feature was introduced in the United States on September 5, 2007. Users can create custom ringtones from songs purchased from the iTunes Store for a small additional fee.
The ringtones can be 3 to 30 seconds long from any part of a song, can fade in and out, pause from half a second to five seconds when looped, or loop continuously. All customizing can be done in iTunes, and the synced ringtones can also be used for alarms. Custom ringtones can also be created using Apple's GarageBand software 4.1.1 or later (available only on Mac OS X) and third-party tools. Custom ringtones are not supported in some countries
