弹指之间
       　 At Your Fingertips 　
       　 　　触控荧幕的应用非常广泛，例如游客导览系统、自动柜员机、销售点终端机、工业控制系统等。在2000年，六家专门厂商加上几家大公司的触控产品部门，总产值高达八亿美元。由于这种介面使用方便、经久耐用，而且花费不高，因此市场还在成长之中。
       　　触控荧幕可依其侦测触控点的物理原理，分为三种：电阻式荧幕，用手指或其他触头轻按就会产生电压；电容式荧幕，手指会吸取微小的电流（常用于笔记型电脑的触控板）。至于第三种波动式荧幕，则是用声波或红外线覆盖整个表面，而手指或触头会阻断这些驻波图样。
       　　电阻式荧幕是历史最久、用途最广，也是价格最低的一种，而且任何触头（无论手指或笔尖）都可以使用。电容式荧幕必须使用手指，或是接有地线的触头，以便传导电流。波动式荧幕则是最新且最昂贵的类型。表面声波荧幕必须用手指或软式触头（例如铅笔上的橡皮擦）轻触，以吸收表面能量；红外线触控荧幕则可使用任何触头。在实际应用上，可以同时选用好几种技术，不过基于各技术的优缺点，通常导致以下的组合：工业控制系统和掌上型电脑Palm Pilot使用电阻式，自动贩卖机使用电容式，自动柜员机及室内资讯站使用波动式。但是大多数人并不清楚，自己所使用的荧幕是什么类型。
       　　沈辉斌任职于美国最大的触控荧幕制造商──位于加州夫利蒙市的易触控系统公司，他提供了以下的辨别诀窍。你可用指甲（而不是皮肤）轻压荧幕，假如荧幕有反应，就可能是电阻式或红外线式荧幕。果真如此，再同时用两根手指分别轻压荧幕上两点。假如游标移到其中一根手指下方，这装置使用的就是红外线（软体只记录第一个接触点）；假如游标移到两根手指之间，荧幕就是电阻式（两个接触点皆有影响力）。假如这个装置对指甲毫无反应，你的下一步还是用两根手指分别轻压荧幕上两点。这时候，如果游标移到其中一根手指下方，那么这荧幕使用的原理是声波；假如游标移到两根手指中间，它就是电容式触控荧幕。
        　　We use touch screens everywhere: tourist kiosks, automatic teller machines, point-of-sale terminals, industrial controls. Half a dozen vendors, plus in-house departments at major manufacturers, produced $800 million worth in 2000. The market is growing because the interfaces are easy-to-use, durable and inexpensive.
       　　Touch screens employ one of three physics principles for detecting the point of touch. Pressing a resistive design with a finger or other stylus raises a voltage. In capacitive models, a finger draws a minute current (this method is often used for cursor pads on notebook computers). In other designs, a finger or stylus interrupts a standing pattern of acoustic waves or infrared lights that blanket the surface.
       　　Resistive screens are the oldest, most widely used and least expensive, and they work with any stylus (finger, pen). Capacitive screens must be touched by a finger or an electrically grounded stylus to conduct current. Wave screens are the newest and most expensive. Surface acoustic wave screens must be touched by a finger or a soft stylus such as a pencil eraser to absorb energy; infrared screens work with any stylus. The different technologies may be used in the same applications, although pros and cons lead to prevalent combinations: resistive screens for industrial controls and Palm Pilots; capacitive screens for slot machines; wave screens for ATMs and indoor kiosks.
       　　Most people are unaware of the type of screen they are using. But tricks can help you tell, according to Frank Shen of Elo TouchSystems in Fremont, Calif., the largest U.S. maker. Push the screen lightly with your fingernail (not your skin). If it responds, it could be resistive or infrared. In this case, place two separated fingers against the screen at the same time. If the cursor moves beneath one finger, the unit is infrared (software registers the first touch); if the cursor moves between the fingers, it is resistive (the points are averaged). If the unit does not respond to your fingernail, again place two separated fingers against it. If the cursor moves beneath one finger, the unit is acoustic wave; if the cursor moves between the fingers, it is capacitive.