A pager is a small telecommunications device that receives (and, in some cases, transmits) alert signals and/or short messages. This type of device is convenient for people expecting telephone calls, but who are not near a telephone set to make or return calls immediately.
A typical one-way pager fits easily in a shirt pocket; some are as small as a wristwatch. A miniature, short-range wireless receiver captures a message, usually accompanied by a beep. (This is why the device is also known as a beeper). The simplest one-way pagers display the return-call telephone number of the person who sent the message. Alternatively, a code can be displayed that indicates which of several designated parties is requesting a return phone call. Sophisticated one-way pagers can display short text messages.
Until recently, pagers were designed as receive-only devices. There are at least two reasons for this. First, if two-way communication is needed, cell phones are available for that purpose. Second, it is difficult to engineer an efficient wireless transmitter that can fit inside a tiny package and provide enough signal range to reach repeaters from all points within the coverage zone.
Despite the engineering challenge, a two-way pager, also called a two-way messaging device or two-way interactive system, has been developed. This system employs large numbers of repeaters, allowing low-power wireless transmitters with subminiature antennas to reach at least one repeater from any location within the coverage area. A typical unit is about the size of a pocket calculator and has a built-in, miniature keyboard and a liquid crystal display (LCD) screen that can display several lines of text and/or simple graphics.
Mobile phones have replaced pagers for most users. However, because they are reliable in some situations where mobile phones are not, pagers are still widely used by essential services personnel, such as those in the medical and emergency-related professions. New uses for pagers have also arisen. For example, restaurants often use pagers to let customers know when their tables are ready.