# Touch Screens **URL:** \ **Category:** Factual Questions\ **Created:** [April 18, 2001, 11:56am UTC](https://boards.straightdope.com/t/touch-screens/62412 "2001-04-18T11:56:31Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![tevya](https://avatars.discourse-cdn.com/v4/letter/t/4491bb/32.png) [@tevya](https://boards.straightdope.com/u/tevya)\ **Post date:** [April 18, 2001, 11:56am UTC](https://boards.straightdope.com/t/touch-screens/62412/1 "2001-04-18T11:56:31Z")
I’m not completely ignorant when it comes to technology, but for the life of me I cannot figure out how touch screens work. I thought at first it was a light sensitive screen and that touching it caused a group of light sensitive cells to go dark indicating to the screen that this was the selected area. However, experiments with blocking the light with the end of a pen failed to produce a selection. Then again, placing a piece of cardboard between the pen and the screen seemed to work. So, can someone explain how the heck these things operate? Right now I’m leaning towards either magic or little gnomes or maybe little magic gnomes. ---
**Author:** ![tevya](https://avatars.discourse-cdn.com/v4/letter/t/4491bb/32.png) [@tevya](https://boards.straightdope.com/u/tevya)\ **Post date:** [April 18, 2001, 12:37pm UTC](https://boards.straightdope.com/t/touch-screens/62412/2 "2001-04-18T12:37:10Z")
It’s not bad enough that I talk to myself out loud. Now I’m having cyber conversations with myself. Anywho, I’m doing a little research and it looks like it may be that touching the screen completes a circuit. This still doesn’t explain why using a pen didn’t work though. Perhaps the area was not large enough or not enough pressure was applied. I’ll get back to me after I’ve done more research. ---
**Author:** ![tevya](https://avatars.discourse-cdn.com/v4/letter/t/4491bb/32.png) [@tevya](https://boards.straightdope.com/u/tevya)\ **Post date:** [April 18, 2001, 1:06pm UTC](https://boards.straightdope.com/t/touch-screens/62412/3 "2001-04-18T13:06:00Z")
This site seems to have some good information: [touch screens](http://www.repairfaq.org/filipg/LINK/F_touchscreen.html#TOUCHSCREEN_005) ---
**Author:** ![Patty\_O\_Furniture](https://avatars.discourse-cdn.com/v4/letter/p/96bed5/32.png) [@Patty\_O\_Furniture](https://boards.straightdope.com/u/Patty_O_Furniture)\ **Post date:** [April 18, 2001, 1:06pm UTC](https://boards.straightdope.com/t/touch-screens/62412/4 "2001-04-18T13:06:54Z")
[Touchscreens.com](http://www.touchscreens.com/compare.shtml): > [@](#): > > Resistive touch technology consists of a glass or acrylic panel that is coated with electrically condictive and resistive layers. The thin layers are separated by invisible separator dots. When operating, an electrical current moves through the screen. > When pressure is applied to the screen the layers are pressed together, causing a change in the electrical current and a touch event to be registered. Magic gnomes is old technology. ---
**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\ **Post date:** [April 18, 2001, 1:13pm UTC](https://boards.straightdope.com/t/touch-screens/62412/5 "2001-04-18T13:13:08Z")
What about elevator call buttons? You know…the ones with a silver up or down arrow on a black background and an orange circle of light around the button that comes on when you press it? They only seem to work with human skin contact. A pen, pencil, if you’re wearing gloves or pretty much anything else doesn’t seem to work. I’ve breathed on them and flicked a lighter next to them to see if they were heat sensitive but that didn’t work either. What make those things go? ---
**Author:** ![tevya](https://avatars.discourse-cdn.com/v4/letter/t/4491bb/32.png) [@tevya](https://boards.straightdope.com/u/tevya)\ **Post date:** [April 18, 2001, 1:13pm UTC](https://boards.straightdope.com/t/touch-screens/62412/6 "2001-04-18T13:13:20Z")
This site seems to be even easier to understand: [more on touch screens](http://www.stanford.edu/~snajmi/touchscreens.htm#How%20TouchScreens%20Work) From that site: \ “Unlike resistive touchscreens, where any object can create a touch, capacitive touchscreens require contact with a bare finger or conductive stylus. When you touch your finger or another conductive object to the screen, current from each corner of the touchscreen is drawn to it. This causes the oscillator circuit in each corner of the screen to vary in frequency depending on where you touched the screen. The frequencies that are produced can be translated into x- and y-coordinates, thus pinpointing the touch event.” I still don’t know how they get the gnomes in there, though. 😉 ---
**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\ **Post date:** [April 18, 2001, 1:36pm UTC](https://boards.straightdope.com/t/touch-screens/62412/7 "2001-04-18T13:36:08Z")
From the same site tevya linked above: > [@](#): > > …capacitive touchscreens require contact with a bare finger or conductive stylus. When you touch your finger or another conductive object to the screen, current from each corner of the touchscreen is drawn to it. This causes the oscillator circuit in each corner of the screen to vary in frequency depending on where you touched the screen. The frequencies that are produced can be translated into x- and y-coordinates, thus pinpointing the touch event.