What is a disadvantage of infra-red optical touch screens?

The correct answer highlights a significant drawback of infra-red optical touch screens: their high manufacturing cost. Infra-red optical technology usually requires multiple components, including sensors and emitters placed around the screen to detect touch through interruptions in projected Infra-red light. This intricate setup can lead to increased production expenses compared to other simpler touch technologies, such as resistive or capacitive touch screens.

In contrast, the other aspects of the technology demonstrate positive traits. For example, durability is typically high due to the absence of a fragile overlay, which is common in some other screen types. Additionally, while cost-effectiveness might not be a feature of infra-red systems specifically, the point directly refers to the benefits that some other touch screen types can have. Lastly, the ability to detect moisture is more a feature of other technologies; infra-red systems are not primarily designed for moisture detection, making this aspect less relevant to the context of disadvantages.