| 单词 | paging system |
| 释义 | paging system 1. A public address, or loudspeaker, system used to make announcements and notify or summon people. In large buildings, paging systems commonly are divided into a number of zones, or coverage areas. Key telephone systems (KTSs) commonly feature voice-over paging, which allows an authorized user to page through the intercom system, which works through the speakers built into the telephone sets. See also intercom and KTS. 2. A radio system designed for alerting or sending messages to individuals. The radio paging system was invented by Al Gross, who also invented the walkie talkie, CB radio, and cordless telephone.The first system, which Gross sold to New York’s Jewish Hospital in 1950, employed a centralized antenna that could broadcast alerts to small, inexpensive pagers, or beepers.A page simply transmitted a unique pager identification number (PID), which was recognized only by the pager being addressed. If that pager were in range, it beeped, hence the term beeper. The response to the page was in the form of a telephone call to the paging company to retrieve a message. The Federal Communications Commission (FCC) approved pagers for consumer use in the United States in 1958. The first consumer pager was the Motorola Pageboy I, which was based on proprietary standards. During the 1970s, an international team developed a standard set of code and signaling formats that evolved into the Post Office Code Standardization Advisory Group (POCSAG) code. Contemporary digital paging systems in the European Union (EU) are based on the European Radio Message System (ERMES) standard. In the United States, the FLEX set of proprietary solutions from Motorola largely has replaced POCSAG and has become the de facto set of standards throughout most of the world, with the exception of Western Europe. Paging systems generally operate over 25 kHz channels in the 900 MHz band. Radio common carriers (RFCs) are regulated providers of public services and are restricted to designated frequencies. Private paging operators (PPOs) are unregulated, but must share unlicensed spectrum with other users in the VHF and UHF bands. A typical page begins with a text message transmitted via e-mail to a centralized network operations center (NOC).The NOC forwards the page to a satellite, which forwards it to a terrestrial network of centralized antennas that forward it to the target pager. Various types of two-way paging (TWP) systems support duplex transmission. See Gross, Al. See also duplex, FCC, page, pager, POCSAG, PPO, radio, RCC, TWP, UHF, and VHF. |
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