TouchScreen FAQ

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[Document Version: 2.06] Last Updated: 3/19/97 - Minor changes 9/25/05

Chapter 1) Introduction

  1.1) About the Author

Original Author: Alan Triggs
Current maintainer: Fil - see form below.

Contributors: David Allen, Gordon S. Hlavenka, .

  1.2) Preface

(From the Editor)

Greetings. This FAQ covers the hardware and software of the hardware touch screen, only. I'd like to make this clear because I get a lot of e-mail from companies that market kiosks and other applications of touch screens - and that information is beyond the scope of this document. If you are, in fact, interested in applications of touch screens (and even turnkey systems), please search for "touchscreen kiosk" on or Google for an EXTENSIVE (and up-to-date) listing of said products and services.

With that said, I am always interested in any companies that produce the actual touch-screen hardware. I will need your company's full contact info, which technology (capacitive, resistive, etc) you market, general (short) description of the typical generic product, destination market, and a typical entry-level price. Please use this .

Chapter 2) How to acquire a touch screen

There are two ways. First, you can buy a kit which mounts on a regular monitor. This could be just a frame, or a thin covering for your monitor. These usually come in all different sizes to fit any monitor. This kit would also include a driver card to emulate a mouse. The other option is to purchase a fully interactive unit, ie: a monitor with a built in touch screen. Most companies can offer you a choice of either. I chose the latter because I figured it was nicer looking, easier to handle, and it was not that much more expensive. The extra expense involved, usually makes it a pretty cheap monitor though.

Chapter 3) How do touch-screens work?

  3.1) Resistive

A Resistive touch-screen consists of a glass overlay which has about 4 layers over it. The distance between these layers and thickness of them is in the micro-meter range. When you touch the screen, the controller senses it and computes X-Y coordinates. These displays are suitable for restaurants, hospitals, and manufacturing facilities. They can be sealed against moisture and dirt, and can be operated by a gloved hand. They are durable, but the 4-5 layers make the screen not as bright as other options.

Speed of response
Light Transmission
Touch Resolution
high (300/inch)
Subject to Drift
Subject to false touches
1 million touches for 4-wire resistive
35 million touches for 5-wire resistive
(has extra layer for durability)

  3.2) Capacitive

Capacitive touch-screens consist of a glass overlay with a thin metallic conductive coating over the surface of the screen. By touching the overlay surface, a user creates a capacitive coupling with the voltage field, drawing a small amount of current to the point of contact. The amount of current drawn from each corner is used to detect the location of the touch. Typically brighter than resistive screens, capacitive touch-screens are sealed to prevent contamination by water and dirt. They cannot be used with a gloved hand. They are subject to drift, thereby requiring calibration now and then and are vulnerable to scratches. Capacitive touch-screens are useful in public information and point-of-sale systems.

Speed of response
Light Transmission
Touch Resolution
high (50/inch)
Subject to Drift
Subject to false touches
>20 million touches

  3.3) Surface Acoustic Wave (SAW)

Surface Acoustic Wave touch-screens consist of a clear glass overlay. Each axis on the overlay has a transmitting and receiving piezoelectric transducer and a set of reflector stripes. The controller sends a 5-MHz burst to the transmitting transducers which convert the signal into surface waves. These are mechanical waves that propagate on the surface of materials such as glass. When the touch-screen it touched, a portion of the wave is absorbed by the finger. This is (somehow) converted to X-Y coordinates by the controller. These touch-screens are very clear since there is nothing but glass. They are bright, stable, can withstand temp, humidity, etc changes. Scratches do not affect the SAW touch-screens but they are do not work well when liquid comes in contact with the screen.

Speed of response
Light Transmission
Touch Resolution
high (30/inch)
Subject to Drift
Subject to false touches
No Limit (tested to over 50 million touches)

  3.4) LED Array

LED Array touch-screens consists of an array of LEDs across the top and one side, and an array of photo transistors across the bottom and other side. These set up a mesh of beams, and when a location is touched, some of the X-Y beams are blocked by the finger. There are no overlays so they are very clear and bright. They are subject to false touches, however, especially since the array is often more than a centimeter above the glass. Flies and dust also create problems.

Speed of response
Light Transmission
Touch Resolution
very low (8/inch)
Subject to Drift
Subject to false touches
Limited to life of LEDs
(which is not very long, IMO)
(From the Editor: Newer LEDs have lives of over 100K hours !!)

  3.5) Pressure Sensing

This is a relatively new "freaky" kind of technology. Nicknamed the "pizza box", in industry, these touch-screens consist of a flat platform, on which you put a monitor. It won Product Of The Year Award from IDN (?) magazine in 1993. The platform acts as the touch-screen, so you can put any monitor on it. The platform consists of a top plate which rests on springs that can sense movement in 3 dimensions. A touch can be measured by the displacement of the springs! This still freaks me out. Since there is no covering, these touch-screens are very clear, bright, scratch resistant, etc. Calibration, however, is time-consuming and difficult. If the monitor is moved at all, the software has to be re-calibrated again. Note the slow response time.

Speed of response
Light Transmission
Touch Resolution
medium (40/inch)
Subject to Drift
Subject to false touches
No data available

Chapter 4) Company Contacts

(From the Editor)

Note: If you represent a company that wants to be or is listed here and you would like me to make some changes here, please send me your info/comments. Thanks!

Well, there's a brief description of each technology... as far as contacts are concerned:

Note: Not in any particular order! (one of these days...)

  4.1) Bitworks, Inc.


Bitworks, Inc. Bitworks, Inc.
#1 Bitworks Way
Prairie Grove, AR 72753
Tel: 479-846-5777

"Designed and tested a 320x240 LCD controller with integrated analog resistive touch screen which could be controlled via an RS232 port. The DSP based system allowed screens and button areas to be predefined to allow quick key entry and display updates."

C, ADSP2105 assembly language
LCD drivers, LCD interfacing, ADSP2105, RS232, RS485, Analog Touch Screens, AtoD, PALs, GALs, Orcad Schematic, Protel for Windows Layout

  4.2) Carroll Touch

Carroll Touch
Technology: Resistive, Infrared, Guided Wave, Capacitive
Tel: (800) 386-8241

  4.3) DBI

Tel: 503-654-6216
They sell touch-screen displays

  4.4) Dynapro

Technology: Resistive
Tel: (414) 365-3555

  4.5) Edmark Corp

Edmark Corp
Attn: Amy Gutmann
6727 185th Ave. N.E.
Redmond, WA 98052
Tel: (206) 556-8825
Tel: (800) 691-2985 (Customer Service)


Edmark Corporation, a leading developer of educational software for students, today announced the release of its newly upgraded TouchWindow touch-sensitive screen. Already in use in approximately 42,000 classrooms throughout the country, the TouchWindow is now compatible with computers running Windows 95. The TouchWindow is also available for Macintosh, Windows 3.1, DOS, and Apple II computers, and is compatible with most of today,s educational software titles. The TouchWindow fits on color or monochrome monitors from 9" to 15".

  4.6) Elo TouchSystems, Inc

Elo TouchSystems, Inc.

[resistive, surface acoustic wave]

Elo TouchSystems, formerly Elographics, has been leading touchscreen development since its founding in 1971. The company pioneered resistive touchscreen technology (AccuTouch), and introduced new touchscreen technology, surface wave (IntelliTouch), in 1987. Elo holds dozens of key patents on both designs.

  4.7) ETC Computers

ETC Computers
Technology: Capacitive
Tel: (510) 226-6250

  4.8) Glasser Whitley Limited (GWL)

Glasser Whitley Limited (GWL)
Attn: John Glasser
Tel: +44 (0)1442-826671
Fax: +44 (0)1442-890694

Glasser Whitley Limited (GWL) provides a full range of touch screen solutions in the UNIX environment, ie workstations, Xterminals and PC-based environments.

With the addition of a touch screen on your monitor, and the loading of our TRIDENT driver software on your host computer, your mouse driven application will be able to use touch as well as mouse without any modification to your application.

GWL is the primary source in Europe for touch screen solutions in the Unix (Workstation, Xterminal & PC-based Unix environments). Our driver software allows mouse driven applications to use touch as well as mouse without ANY application software modifications. Our solution set will cover all your needs. We can provide 15", 17" & 21" turn key monitors already configured with touch. We can provide touchscreen driver software to customers who prefer to purchase their touchscreen hardware directly from other sources. Driver software is available at quantity pricing or site/licenses project.

Currently Supported Platforms:

  4.9) Groovy Technology Corp

Groovy Technology Corp
7F, 278-2, Chung Ching N. Rd.
Sec. 3, Taipei
Fax: 2-5949489

They make: Touch Screen Kits, Touchscreen Monitors.

  4.10) Hi-Tech Instruments, Inc

Hi-Tech Instruments, Inc
3727 Greenbriar, Suite 117
Stafford, TX 77477
Tel: (713) 980-9040
Fax: (713) 980-2524

We manufacture the resistive touch screens, any sizes. Hundreds of 15" integrated touch monitors are in stock. We have both ISA card and serial COM controller.

  4.11) Interaction Systems, Inc

(From Paul Guttmann)

Interaction Systems, Inc.
Watertown, MA 02172
Tel: (617) 932-0700 NOTE CORRECTED #!

They make clear capacitive touch screens that are designed to be fit over existing LCD or CRT displays. Capacitive only. Small company I believe.

  4.12) Keytec

Technology: Resistive
Tel: (800) MAGIC89
Tel: (800) 624-4289
Fax: (972) 234-8542

  4.13) MicroTouch in Massachusetts

MicroTouch in Massachusetts
Technology: Capacitive, Resistive, Pressure-Sensing
Tel: (800) 642-7686
Tel: (508) 659-9000 (??)

These people are the leaders in the US, and maybe worldwide. They deal in Resistive, Capacitive, and Pressure-Sensing. They have the biggest range of screens and kits, and possibly the best services.

  4.14) Personal Computing Tools

Personal Computing Tools
Tel: 800 767 6728

They have a retro-fit screen which can be used with monitors 13 to 15 inches. It's called a Magic Touch and is used with a finger or included stylus. It clips to the front of the monitor and plugs into the serial port to emulate a mouse. Price is $279, expensive for a mouse, but, cheaper than a touch screen monitor.

  4.15) TekVision

Technology: Resistive, Capacitive, Surface Acoustic Wave
Tel: (800) 466-8005

  4.16) Touch Technology

Touch Technology
5524 Bee Caves Rd.
Austin, TX 78746
Tel: (512) 328-9284
Tel: (512) 990-9700

This is the company we got our screen from. They offer capacitive, and maybe some of the others. We found them the cheapest by far. We got a 14" Capacitive touch screen (complete with monitor) for $695. Similar specs with ELO and MicroTouch would have cost over $1000. ELO warned us of dealing with Touch Technology. They said to be careful of what we get, which caused us to ponder the cheap price. So far however, we have no problems, leading me to believe that it was just sour grapes from ELO. Also, their driver will emulate a mouse with the touchscreen.

  4.17) Transparent Devices

Transparent Devices
Tel: 805-499-5000

They sell transparent touch-screen overlays; you put them over whatever display you have available.

USA Address:
Trident Systems Inc.
10201 Lee Highway, Suite 300,
Fairfax, VA 22030
Tel: (703) 273-1012
Fax: (703) 273-3763

Europe Address:
Glasser Whitley Ltd.
Tring House, 77-81 High Street, Tring,
Herts HP23 4AL.
Tel: +441-442-826671
Fax: +441-442-890694

Trident is a small business in Farifax, Virginia. The company has spent the last decade solving information technology challenges. We specialize in solution approaches. That is, we first learn the specifics of the customer's problem; next, we examine the alternatives; after this, we execute the plan developed in conjunction with the customer; finally we deliver, install, and support the solution. Trident provides:

  1. Systems Engineering services (e.g., sys design and assembly, test and integration services, custom software development, and state of the art computer centers);
  2. System design assessment & prototyping;
  3. System Integration, testing & support;
  4. Advanced Technology applications.

"It is in the advanced technology solutions that we have developed the widest array of Unix systems and non-Unix systems solutions for touch screen implementation. Within the Unix community, Trident is alone in offering touch screen solutions. We offer full systems solutions (system hardware and touch implementation), touch monitor solutions (turn-key monitors configured with touch), touch screen hardware solutions (touch screen hardware and driver software), touch screen driver software (over 24 Unix drivers for most available touch screen hardware technologies), and custom touch screen software development services."

  4.18) Troll Touch

Troll Touch
Technology: Resistive
Tel: (800) 201-1160

  4.19) Vivid Technology

Vivid Technology
Technology: Infrared
Tel: (800) 848-4385

  4.20) VL Electronics

VL Electronics
Tel: 213-738-8700
They sell graphic touch-screen displays.

  4.21) V.S.M.

1, Les Amandiers
Pelissane, 13330
Tel: 011-33-90-55-06-25
Fax: 011-33-90-55-32-46

TSI (Touch Screen Interface) is a complete hardware and software touchscreen solution for SGI workstations.

Based on Surface Acoustic Waves technology, it allows response on X-, Y-, and Z- axis. Solutions are available for most screens (flat, spherical, cylindrical) in different dimensions. VSM provides full installation on your monitor, or can provide complete TSI Integrated solutions compatible with SGI. TSI is connected through serial RS232 port.

Software is easily integrated in IRIX, thus allowing, without modification, all SGI tools or applications to run indifferently with the touchscreen or with the mouse at the same time. It includes calibration and test facilities.

  4.22) WinSurfer Orders

WinSurfer Orders
Office of Technology Liaison
4312 Knox Road
University of Maryland
College Park, MD 20742
Tel: 301-405-4210
Fax: 301-314-9871

New General Selection Touchscreen Support Library (NGS)

HCIL has long been a leader in touchscreen applications and research. Years of study have produced innovative techniques and algorithms for operating a touchscreen user interface. The NGS library has been developed at HCIL for constructing our Borland C language user interfaces on IBM PC and IBM AT compatible machines. NGS has been refined by our 5 years of research and has been in user internally for over two years.

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