Apple's iPod has received praise from all corners for its elegant design and ease-of-use, but the one aspect of the digital-music player that neatly ties these two features together, the scroll-wheel, wasn't actually designed by the company.

Touch-pad experts Synaptics designed the scroll-wheel of Apple's iPod, albeit in accordance with Apple's stringent design requirements, reveals MP3 Insider.

Synaptics is responsible for making 70 per cent of the touch-pads on laptops The article notes that when you move your finger more quickly across the touchpad on a laptop, the mouse moves more quickly across the screen, "iPod's scrollwheel works via the same principle, which is one reason it's so effective at blasting through long song lists," says the report.

The article plots the evolution of the scroll-wheel from the original one that physically rotated and was not touch-sensitive; to the motionless, touch-sensitive scroll-wheel that enabled Apple to make a thinner iPod; and finally to the click-sensitive scroll-wheel that allows for song-scrolling and playback control.

Synaptics' contract with Apple means it cannot offer the round touch-pad technology to any other MP3 companies, but recently it has devised a straightened-out version of it for Creative's Zen Touch.