Inner Workings: Inside a Touchscreen Remote

True, it's not as cool a user experience as moving holographic frames in midair, like Tom Cruise did in Minority Report. But admit it: You get the slightest thrill when you work a touchscreen. And if that screen just happens to be built into a remote control, well, you feel as finger-empowered as E.T.

So how is it that touchscreens give you such great command, while laying your paws on regular old TV screens gives you nothing but smudgy fingerprints? The answer depends on which screen technology you're talking about.

Touchscreen home theater remotes operate via a resistive overlay. On top of the LCD screen rests electrically conductive transparent plastic with a conductive film coating. On top of that, separated by spacer dots, lies another plate with conductive coating underneath. When you press your finger - or stylus, pointer, whatever - on the screen, the top layer flexes at the pressure point, making contact with the bottom, charged plate. This closes a circuit and introduces resistance to the curent flow below. Which part of the screen you touch affects the voltage flow on the bottom plate, allowing two metal strips running perpendicular to the frame's edge to calculate your finger's position. This is then synced with the LCD beneath.

In contrast, the touchscreen technology typically used in ATMs and airport check-in kiosks is called capacitive or conductive. With these screens, there's just one extra plate, through which a current passes. Touch it and your finger draws some of the current. (It's a small current, so there's no danger of electrocution.) Sensors stationed at the plate's four corners measure the charge levels to calculate your finger's position, based on how you've interrupted current flow.

So how can you tell whether you're using a resistive or conductive touchscreen? It's easy, explains Eric Smith, chief technology officer at Control 4, which uses resistive technology in its Wireless Touch Screen remote. "Try using a stylus or even a fingernail on the screen," says Smith. "If it still functions, then it's not conductive, since that technology requires your human skin to work."

That makes us wonder which way Steve Jobs likes to use his fingers. Rumors of the alleged next entry in the iPod family have been burning up the tech blogs. It will be about the same size as a video iPod, but with an LCD covering the front that's operated by touch tech. If this thing becomes a reality, what will Apple call it? How about the iPod Macintouch?

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