Callertone Innovations [NPE] filed three separate suits against ClearSky Mobile, LiveWire Mobile, MetroPCS, United States Cellular, and Zed, 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 has filed seven prior suits since October 22, 2011 against Alltel, AT&T, Boost Mobile, Sprint Nextel, T-Mobile, Verizon, and Virgin Mobile.  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. 11/1, District of Delaware, 1:2011cv01066; 1:2011cv01067; 1:2011cv01068.