Apple this week purchased a patent for the iPhone from BT.

The patent (US patent 6,956,564) covers sensing technology originally invented by Lyndsay Williams for BT in 1997.

The technology was originally deployed in a touch-sensitive computer called SmartQuill. This was capable of handwriting recognition, and could be used to write documents on paper the computer would then remember and store.

As it applies to the iPhone, the patent covers the devices designation as a portable computer that's responsive to movement and produces an electrical output signal representative of such movement.

SmartQuill carried a small screen that offered different views as the device was turned around. The patent purchase could be designed to protect Apple's iPhone's movement detection sensor, which moves the screen and changes the representation offered on screen when iPhone is moved around.

Williams is now managing director of Girton Labs.