CRBT stands for Color Ring Back Tone. Instead of hearing the traditional tiring, tiring ring tone when calling someone, CRBT lets phone user ply their favorite tune, sound, jingle to incoming callers. Users can select their ring tone from a large pool supplied by a content provider through a Web or IVR server.
The most important distinction between CRBT and other services is that this network-based solution is independent of both handset and subscriber identity modules (SIM). Users are not required to have the newest phone or a specific brand of phone.