Callertone Innovations [NPE] filed six separate suits against Alltel, Boost Mobile, Sprint Nextel, T-Mobile, Verizon, and Virgin Mobile, alleging that defendant’s ring-back tones infringe two patents related to associating an audio message with an incoming call.  Ring-back tones are audio messages selected by a phone subscriber to personalize the ringtone that callers hear when they place a call to the subscriber’s phone number.  Callertone filed one prior suit on October 22, 2011 against AT&T.  The patents-in-suit were issued to Network Directory Sciences (an entity that appears to be related to Mount Hamilton Partners via assignment records), and were assigned to Callertone in February 2011. 10/28, District of Delaware, 1:2011cv01033; 1:2011cv01034; 1:2011cv01035; 1:2011cv01036; 1:2011cv01039; 1:2011cv01044.