During the old days, the function of doorbell is similar to knocking at the door and it is only available to the wealthy; while nowadays it can be found anywhere. And it possesses much more usages.
Among the doorbells we apply to, the most common ones are electric ones. Several years ago, a so-called "electronic doorbell" was very popular. Then, the intercom doorbell appeared and helped people to distinguish their visitors by voice. In addition, now some intercom doorbells are accompanied with web cams which enable people to see their visitors.
Actually, some people begin to employ doorbells to more fields. For example, some store hang a windbell as a doorbell on the door to welcome the customers. By installing more trigger corresponding sensors, some people use doorbells as gas leak alarm, fire alarm and so on. With the development of technology, we will explore more usages of doorbells.
A doorbell may seem very common and simple, but our creativity is infinite. Just do it now!
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