While Apple and iPhone trademark">Cisco may have already settled their differences, the iPhone could very well come under fire again. According to Tech2, Quantum Research has threatened to sue Apple if it finds that the company has infringed on its touch-screen patent.

Quantum, a UK based touch-sensor manufacturer, is currently checking the iPhone for any indications that Apple is using any of their patented touch-screen technologies. Duncan Bryan, licensing director at Quantum Research said that the iPhone's description suggests that it uses a rear-surface touch screen and has proximity sensing which can tell if it is held to the ear. Both are Quantum capabilities.

Tech2 notes that this is Quantum's second attempt to warn Apple about patent infringement. Quantum filed a patent-infringement lawsuit against the Cupertino-based company in December 2005 over Apple's use of Quantum's patented charge transfer technology in the iPod Nano's wheel control. The December 2005 suit is still under process.