1) What is a touch screen?
Answer. A touch screen is a means of using computer applications and choosing options within the application without using a mouse. You replace the mouse click functions by actually touching your selection on the monitor itself.

2) What is the advantage of that?
Answer. Because a well designed application, one specifically developed to use a touch screen, can prompt a user through the necessary choices needed to use the application. There is no need to learn special commands. This is important when the user is not computer literate (public access information kiosks, ticket machines) or if there are large numbers of repeated routine tasks (such as order entry in a fast food environment). Because a touch screen application is so easy to use training time is reduced greatly, which is important in businesses with staff retention difficulties. Also because there is no mouse there is no need to worry about space requirements or vandalism.

3) How do they work?
Answer. There are actually several different technologies used to produce the touch screen "effect". All are similar in that selections are made by touching the monitor screen surface itself. The major technologies are (in alphabetical order) Capacitive, Infrared, Resistive, and Surface Acoustic Wave.

4) Are they all the same?
Answer. No, the only similarities are the means of operation, and the use of sensors and controllers to operate. Each approaches the function from a different manner.

5) What is a sensor?
Answer. This is the touch screens "nervous system". The sensor is used to determine the position of the operators touch. This can be either a specially designed glass sheet or LED's and optical sensors positioned around the outside of the monitor display area.

6) What is a controller?
Answer. This is the touch screens "brain". Information from the sensor is processed and relayed to the computers CPU to activate the desired function.

7) How do the different technologies work?
Answer. With CAPACITIVE touch screens the sensor consists of a glass sheet with a SINGLE conductive layer bonded to it. Electrical energy is applied evenly to the conductive layer. When touching the sensor the operator becomes part of the circuit, closing the circuit allowing energy to flow. As electrical current flows greatest where resistance is least, the controller measures these flows from the edges of the sensor and determines the position of the touch from this information. Because the operator is essentially part of the circuit, the touch MUST be conductive, thus using gloves or objects to activate the screen will not work with this technology, only a finger will work.

RESISTIVE sensors are sheets of glass with TWO layers of conductive material bonded to the surface. Electrical energy is applied to one of these surfaces. Separating the two layers are tiny insolating beads. When you touch the screens surface you overcome this separation bringing the two layers together, thus closing the circuit and allowing electrical energy to flow. The controller measures current flows and position is determined with this information.

SURFACE ACOUSTIC WAVE (SAW) sensors are sheets of glass that have ultrasound transducers (speakers) and transceivers (microphones) positioned around the edges of the pane. When beginning operation the touch screen creates a field of ultrasound energy across the sheet of glass, the controller uses this field to create a digital map of the surface of the sensor. The controller then uses that map as basis of comparisons it makes several times a second. Any changes are recognized and sent to the CPU to be acted upon as input.

INFRARED sensors are essentially a ring placed along the outside of the display area of the monitor. Along two sides are infared light emitting diodes (LEDS), along the opposite side are infared sensors. This creates a grid of invisible light that allows the controller to determine touch position when the grid is broken.

8) Is one technology better than the others?
Answer. All touch screen technologies accomplish the same thing, input selections without use of a computer mouse. All have features and benefits different from each other. With my personal experience the decision to use one technology over another should be based upon 1) the physical environment of the installed equipment. 2) the budget the client has for the equipment. Many times when given a choice a client will chose less expensive hardware for the prototypes and then migrate to the more expensive hardware for the product roll out. In a nutshell the good and bad are (by technology).

Resistive: Pro: Most affordable, tested stable and reliable product, can be used with gloves on hands or stylus. Con: Decreases light output from monitor, susceptible to damage from scratches to the sensor, can be activated by any touch.

Capacitive: Pro: Stable and reliable, helps prevent accidental activation, less susceptible to damage, only a finger touch will activate Con: Less affordable than resistive, still subject to scratches, reduces screen brightness (less than resistive though).

Acoustic (SAW): Pro: Stable, reliable, activated by finger touch also, almost no brightness reduction of monitor, impervious to scratches. Con: More expensive, somewhat harder to install.

Infrared: Pro: Stable, reliable, impervious to scratches, no brightness reduction, easy to install Con: Activated by whatever breaks the beam, higher component cost.