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A pager (also known as a beeper or bleeper) is a wireless telecommunications device that receives and displays numeric or text messages, 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 6 oz (200 g) pager that would receive phone messages within 25 mi (40 km) 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 continued to expand, until the early 1990s. However, by the mid-1990s, as cellular technologies became cheaper and more widely available, advanced services began to displace paging as a commercial product. Today, pagers exist largely as niche products, finding preferential use in applications such as hospitals, public safety, and retail locations where their simplicity, high reliability, and low cost represent significant advantages.
Paging systems are operated by commercial carriers, often as a subscription service, and they are also operated directly by end users as private systems. Commercial carrier systems tend to cover a larger geographical area than private systems, while private systems tend to cover their limited area more thoroughly and deliver messages faster than commercial systems. In all systems, clients send messages to pagers, an activity commonly referred to as paging. System operators often assign unique phone numbers or email addresses to pagers (and pre-defined groups of pagers), enabling clients to page by telephone call, e-mail, and SMS. Paging systems also support various types of direct connection protocols, which sacrifice global addressing and accessibility for a dedicated communications link. Automated monitoring and escalation software clients, often used in hospitals, IT departments, and alarm companies, tend to prefer direct connections because of the increased reliability. Small paging systems, such as those used in restaurant and retail establishments, often integrate a keyboard and paging system into a single box, reducing both cost and complexity.
Paging systems support several popular direct connection protocols, including TAP, TNPP, SNPP, and WCTP, as well as proprietary modem- and socket-based protocols. Additionally, organizations often integrate paging systems with their Voice-mail and PBX systems, conceptually attaching pagers to a telephone extensions, and they set up web portals to integrate pagers into other parts of their enterprise. A paging system alerts a pager (or group of pagers) by transmitting information over an RF channel, including an address and message information. This information is formatted using a paging protocol, such as 2-tone, 5/6-tone, GOLAY, POCSAG, FLEX, ERMES, or NTT. Two-way pagers and response pagers typically use the ReFLEX protocol.
Pagers themselves vary from very cheap and simple beepers, to more complex personal communications equipment, falling into eight main categories:
Modern paging systems typically use multiple base transmitters to modulate the same signal on the same RF channel, a design approach called simulcast. This type of design enables pagers to select the strongest signal from several candidate transmitters using FM capture, thereby improving overall system performance. Simulcast systems often use satellite to distribute identical information to multiple transmitters, and GPS at each transmitter to precisely time its modulation relative to other transmitters. The 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.
Pagers are still in use today in places where mobile phones typically cannot reach users, and also in places where the operation of the radio transmitters contained in mobile phones is problematic or prohibited. One such type of location is a large hospital complex, where cellular coverage is often weak or nonexistent, where radio transmitters are thought to interfere with sensitive medical equipment and where there is a greater need of assurance for a timely delivery of a message. Another is a facility handling classified information, where various radio transmitter or data storage devices are excluded to ensure security.
The 2005 London bombings resulted in overload of TETRA systems by the emergency services, and showed that pagers, with their absence of necessity to transmit an acknowledgement before showing the message, and the related capability to operate on very low signal levels, are not completely outclassed by their successors.
Volunteer Firefighters, EMS, and Rescue squad members usually carry pagers to alert them of emergency call outs for their department. These pagers receive a special tone from a fire department radio frequency.
Restaurant pagers are in wide use today. These are generally from the beeper category. Customers are given a portable receiver that usually vibrates, flashes, or beeps when a table becomes free or when their meal is ready. Companies like HME Wireless and Jtech are known leaders of the industry with smaller companies making up the rest of the market.  Successful restaurant companies such as Crave Restaurant group 
Pagers have been popular with birdwatchers in Britain and Ireland since 1991, with companies Rare Bird Alert and Birdnet Information offering news of rare birds sent to pagers that they sell.
The U.S. paging industry generated $2.1 billion in revenue in 2008, down from $6.2 billion in 2003.
In 1962 the Bell System—the U.S. telephone monopoly colloquially known as "Ma Bell"—presented its Bellboy radio paging system at the Seattle World's Fair. Bellboy was the first commercial system for personal paging. It also marked one of the first consumer applications of the transistor (invented by Bell Labs in 1947), for which three Bell Labs inventors received a Nobel Prize in Physics in 1956. Solid-state circuitry enabled the Bellboy pager, about the size of a small TV remote device, to fit into a customer's pocket or purse, quite a feat at that time. The Bellboy is a terminal that notifies the user when someone is trying to call. When the person receives an audible signal (a buzz) on the pager, he finds a telephone and calls the service center, which informs him of the caller's message.
The Bell System Bellboy radio pagers each used three tuned reed receiver relays, each relay tuned to one of 33 different frequencies, selectively ringing a particular customer when all three relays were activated at the same time—a precursor of DTMF.
The ReFLEX protocol was developed in the mid 1990s.
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As is the case with many new technologies, the functionality of the pager shifted from necessary professional use to a social tool integrated in one's personal life. Within a short time span, pagers evolved from a tool for “technocratic elites” to a tool used by “kids living in the projects.”
During the rise of the pager, it became the subject of various forms of media; most notably in the 1990s hip-hop scene. Upcoming mainstream artists such as Ice Cube, Method Man, and A Tribe Called Quest began referencing forthcoming mobile technologies, in particular the pager. A Tribe Called Quest's single 'Skypager' directly speaks of the importance of such a wireless communication device. Q-Tip conveys that the skypager "serves an important communicative function for a young professional with a full calendar". Three 6 Mafia's "2-Way Freak" and the smash hit "Bug a Boo" from Destiny's Child also make reference to pagers.
Pagers were a featured segment on the "1991" episode of I Love the '90s: Part Deux. The segment explored the device's entrance into mainstream pop culture; it also discussed the humorous use of calculator spelling to send messages through the devices.
The growing popularity of cellphones in the early 21st century was accompanied by a corresponding decline in pager use by the general population. This shift accounts for Sam Flynn's amusement when Alan Bradley says "I was paged last night" in Tron: Legacy. Likewise, the 30 Rock sitcom character Dennis Duffy attracts disdain and mockery for his career as a pager salesman.
Associate superintendent for Dade County Public Schools in Florida James Fleming once called them "the most dominant symbol of the drug trade" and schools have previously forbidden students from carrying them because of the ease with which they could be "used to arrange illegal drug sales". The use of pagers by the Barksdale crew of drug dealers in Baltimore features prominently in the first season of the HBO cop drama The Wire.
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Pagers also have privacy advantages compared with cellular phones. Since a one-way pager is a passive receiver only (it sends no information back to the base station), its location cannot be tracked. However, this can also be disadvantageous, as a message sent to a pager must be broadcast from every paging transmitter in the pager's service area. Thus, if a pager has nationwide service, a message sent to it could be intercepted by criminals or law enforcement agencies anywhere within the nationwide service area.
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Many paging network operators now allow numeric and textual pages to be submitted to the paging networks via email. This is convenient for many users, due to the widespread adoption of email; but email-based message submission methods do not usually provide any way to ensure that messages have been received by the paging network. This can result in pager messages being delayed or lost. Older forms of message submission using the Telelocator Alphanumeric Protocol involve modem connections directly to a paging network, and are less subject to these delays. For this reason, older forms of message submission retain their usefulness for disseminating highly-important alerts to users such as emergency services personnel.
In the United States, pagers typically receive signals using the FLEX protocol in the 900 MHz band. Commercial paging transmitters typically radiate 1000 watts of effective power, resulting in a much wider coverage area per tower than a mobile phone transmitter, which typically radiates around 0.6 Watts per channel.
Although 900 MHz FLEX paging networks tend to have stronger in-building coverage than mobile phone networks, commercial paging service providers will work with large institutions to install repeater equipment in the event that service is not available in needed areas of the subscribing institution's buildings. This is especially critical in hospital settings where emergency staff must be able to reliably receive pages in order to respond to patient needs.
Unlike mobile phones, most one-way pagers do not display any information about whether a signal is being received or about the strength of the received signal. Since one-way pagers do not contain transmitters, one-way paging networks have no way to track whether a message has been successfully delivered to a pager. Because of this, if a one-way pager is turned off or is not receiving a usable signal at the time a message is transmitted, the message will not be received and the sender of the message will not be notified of this fact. In the mid-1990s, some paging companies began offering a service, which allowed a customer to call their pager-number, and have numeric messages read back to them. This was useful for times when the pager was off or out of the coverage area, as it would know what pages were sent to you even if you never actually received the page.
Other radio bands used for pagers include the 400 MHz band, the VHF band, and the FM commercial broadcast band (88-108 MHz). Other paging protocols used in the VHF, 400 MHz UHF, and 900 MHz bands include POCSAG and ERMES. Pagers using the commercial FM band receive a subcarrier, called the Subsidiary Communications Authority, of a broadcast station.
On-site paging systems in hospitals, unlike wide area paging systems, are local area services. Hospitals commonly use on-site paging for communication with staff and increasingly for contacting waiting patients when their appointment is due. These offer waiting patients the opportunity to leave the waiting area, but still be contacted.
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