Apple has been hit by a second legal suit following its launch of the iPhone.

SP Technologies in Florida is claiming that the touch screen on the iPhone infringes a patent it took out in 2000 and was granted in 2004 for "Method and medium for computer readable keyboard display incapable of user termination".

The patent covers the use of 'soft keyboards', where a keyboard can be activated on screen without any hardware. The timing and target of the suit is therefore slightly odd as many devices use such a system.

"The input area may contain a keyboard which is an image map," the patent reads.

"External programming may selectively access the input area through a dynamic link library. The input area has no task bar and may not be minimized, maximized, or deleted. Therefore, the input area becomes an integral component and provides the user with a constant and reliable method of inputting information into the computer program."

This is the second law suit the iPhone has faced. Cisco has already sued over the iPhone, claiming it holds the rights to the name, but has since settled the issue.