What is Pager?

Legal Definition
A pager (also known as a beeper) is a wireless telecommunications device that receives and displays numeric messages and/or receives and announces voice messages. One-way pagers can only receive messages, while response pagers and two-way pagers can also acknowledge, reply to, and originate messages using an internal transmitter. Pagers operate as part of a paging system which includes one or more fixed transmitters (or in the case of response pagers and two-way pagers, one or more base stations), as well as a number of pagers carried by mobile users. These systems can range from a restaurant system with a single low-power transmitter, to a nationwide system with thousands of high-power base stations.

One of the first practical paging services was launched in 1950 for physicians in the New York City area. Physicians paid $12 per month for the service and carried a 200-gram (7 oz) pager that would receive phone messages within 40 kilometres (25 mi) of a single transmitter tower. The system was manufactured by the Reevesound Company and operated by Telanswerphone. In 1960, John Francis Mitchell combined elements of Motorola's walkie-talkie and automobile radio technologies to create the first transistorized pager, and from that time, paging technology continued to advance, and pager adoption still continues to expand, as of July 2016.

In the 2000s, the widespread availability of cellphones and smartphones has greatly diminished the pager industry. Nevertheless, pagers continue to be used by some emergency services and public safety personnel, because modern pager systems' coverage overlap, combined with use of satellite communications, can make paging systems more reliable than terrestrial based cellular networks in some cases, including during natural and man-made disaster. This resilience has led public safety agencies to adopt pagers over cellular and other commercial services for critical messaging.
-- Wikipedia
Legal Definition
A pager is a small electronic device that was used for relaying small messages from one pager to another. Communication is generally one way. However, with the advent of mobile phones, pagers have significantly declined in popularity.