Free ringback tones can be obtained through various websites. Some applications that provide free ringback tones are available for Android devices. Cellular carriers also offer ringback tones for a fee.
Ringback tones are heard by callers while they wait for calls to be answered. The sound lets the caller know that the call has connected and is ringing for the receiving party. The ringback tone is not synchronized with the ringing heard by the call recipient. Ringback tones are usually hosted on a phone company switch and transmitted in real time. They are not saved on the phone being called. The standard ringback tone in North America lasts 2 seconds with a 4-second pause between tones. Standard tones can be replaced with music, advertising or other audio content.