You call your friend's cell phone.  You wait briefly as the system recognizes your number and also your friend's.  Once that happens, in most cases, you'll start hearing either a busy signal (bawmp-bawmp-bawmp) or a ringback tone.

But, just as people may customize the sounds their phones make when calls come in to them, your friend may have a non-standard ringback tone, such as a sample from a popular song, either for free or by paying extra.

The Federal Circuit grappled last week with a patent dispute over a software algorithm and method for customizing what you hear when you call your friend.  Ring Plus accused Cingular (now AT&T Wireless) of infringing the patent with its Answer Tones service.  The district court granted summary judgment of non-infringement against Ring Plus on the ground that its patent required the system to determine the busy or non-busy status of the receiving party's phone before starting to play the custom sound.  But Cingular's offering began playing the Answer Tone before performing the busy/non-busy check.  The Federal Circuit affirmed, agreeing that the patent claimed only a method for playing custom sounds after the busy/non-busy check.  Ring Plus, Inc. v. Cingular Wireless Corp., No. 09-1537 (Fed. Cir. Aug. 6, 2010).

The panel also reversed summary judgment for Cingular on its inequitable conduct defense and affirmed the district court's decision not to disqualify Cingular's counsel.