What is PAGER
PAGER is a subscriber end electronic device in a paging communication system that is capable of receiving brief messages usually in the form of numeric digits representing phone numbers. The mode of communication that takes place in a pager system is simplex i.e. the pager device can only receive information and can’t send it. The messages received on a pager are usually to notify a subscriber regarding the need to call a particular number.
In modern paging systems, information like stock quotations, weather broadcasting etc. is also received on pagers. Every pager has a unique pager access number that is used to send messages to it through a telephone or a modem.
In a paging system, the backbone of the system in the form of a switching network is connected to the Public Switching Telephone Network (PSTN). This backbone network receives the messages for various pagers known as pages and then broadcasts these messages on the whole system through the use of base station antennas.
A page is broadcasted by the various base station antennas of the system at the same instant of time and this process is known as simulcasting. Now various pagers tuned at the transmitting frequency of the base station antennas receive this message. But the pager access number associated with the message causes only the correct pager to acknowledge this message while the others discard it.
The paging device consists of a passive receiver along with a demodulation circuitry and a display usually in the form of a small LCD. There are also pagers that are capable of receiving voice messages and these contains in addition to the text pagers a microphone along with audio processing circuitry consisting of various filters and amplifiers.
As stated above, the paging system consists of a backbone network supported by a number of base stations. These base stations strive to provide maximum coverage. Therefore high transmission power and low data rates are the main characteristics of a paging system. A recent advance in pager technology is the use of Satellite systems to deliver the one way page messages in place of a terrestrial cellular based system. The Satellite technology is much more reliable than in terms of terrestrial one. In practical systems today, terrestrial technology is used to fill the holes in coverage of the satellite technology.
Pagers systems are most useful where cellular mobile coverage is not available or where mobiles be used such as a hospital environment where electromagnetic waves of a cellular mobile network can interfere with the working of sensitive medical equipment.