Pager

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Pager

Written by goldeneggs

Thursday, 06 November 2008 06:47

A Pager (sometimes referred as a Beeper) is personal telecommunications device used request a phone call from a pager subscriber and/or receive simple text communications in the form of e-mail and SMS. Pagers exist as one-way numeric and alphanumeric models that only receive incoming communications and two-way alphanumeric models capable sending e-mails and SMS messaging.
Until the popular adoption of mobile phones in the late 1990s, Pagers fulfilled the role of a common personal and mobile communications. As of 2007, Pagers have since fallen into obsolescence and preserved only by niche markets of emergency service personnel and information technology support

Function and Operation

The front end of a numeric Pager

A Motorola alphanumeric pager used in Brazil in the '90s, operated by Teletrim

Paging is a subscription service offered in a variety of plans and options to meet the needs of a subscriber and the type of device used. In general, all pagers were given unique phone numbers while alphanumeric pagers with given an e-mail address usually consisting of the phone number.
Upon calling a phone number assigned to a pager, the calling party would reach a recorded greeting with an option to leave voice mail or send pager codes. Almost instantaneously, the paged person would receive an alert emanating from the pager with the phone number to return the call and/or a pager code. In the case of e-mail paging, the text would be displayed.

Numeric pagers are the simplest of the type of devices offering only a numeric display of the phone number to be called and pager codes

Alphanumeric Pagers are essentially modified versions of numeric pagers with sophisticated display to accommodate text. These devices would be given an e-mail address to receive text messages.

Two-way Alphanumeric Pagers are alphanumeric pagers with the ability to send text messages typed in with a small keyboard.

Most modern paging systems use simulcast delivery, by satellite controlled networks. This type of distributed system makes them inherently more reliable than terrestial based cellular networks for message delivery. Many paging transmitters may overlap a coverage area, where in contrast cellular systems are built to fill the holes. When terrestial networks go down in an emergency, satellite systems continue to perform. Because of superior building penetration and availability of service in disaster situations pagers are primarily used by life saving first responders.

Pager use in the 21st Century

A Skyper pager that is in use for HAM Radio

Pagers are still in use today in places where mobile phones typically cannot reach users and in places where the operation of 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, and where radio transmitters are suggested to interfere with sensitive medical equipment. Some common environments pagers are still used in are:

Pagers remain in use to notify emergency personnel. For example, they are required to be used by UK lifeboat men and retained firefighters.

A pager that is in use for emergency services

Pagers are mostly carried by staff in medical establishments, allowing them to be summoned to emergencies.

Pagers are also widely used in the IT world, especially in cases where on-call technicians cannot rely on more modern cellular telephone systems. A good example would be in a cellular telephone company, where a service interruption in the cellular network would also mean that it would not be possible to notify a technician due to the outage in the network. Therefore, in these companies, engineers are usually equipped with a pager that uses another telco's mobile network to ensure reachability in case of emergency.

Additionally, Pager technology is now applied to irrigation control systems, and traffic signals.

Security

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. But 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.

Technical Information

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 Telocator Alphanumeric input Protocol 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.
Common paging protocols include TAP, FLEX, ReFLEX, POCSAG, Golay, ERMES and NTT. Past paging protocols include Two-tone and 5/6-tone.
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 Watt 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.
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.

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