A one-way radio selective calling system without voice.This is a system that converts the number of the paged user and the message of the calling user sent from the automatic telephone switching network into a digital signal of a certain code type and format, transmits it to each base station through the data circuit, and sends it to the called pager by the base station paging transmitter.The receiving end is a plurality of high-sensitivity receivers (commonly known as pocket bells) that can be carried by users.
Chinese name
Wireless paging system
Foreign name
Wireless paging system
Genus
One way selective calling system without voice
Information
Automatically ring, display digital or Chinese characters
When the receiver receives a call, it will automatically ring, display numbers or Chinese characters, and transmit specific information to the user.
The wireless paging system can be divided into two categories: dedicated system and public system.Special systems are mostly manual.Generally, there is a wired telephone near the console.When the operator receives a call from a wired user for a pocket bell, he/she will connect and code it, and then send it to the wireless transmitter through the encoder for calling;The pocket ring rings automatically after receiving the call.The utility system mostly adopts manual and automatic modes.
development
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In 1968, Japan launched an analog paging system on the 150 MHz mobile frequency band, which only sends notification tones and messages by audio.In 1973, the United States launched a digital paging system on the 150MHz and 450MHz mobile frequency bands.In 1978, Sweden used digital paging systems in the FM broadcast band of 87.5~104MHz and Japan in the mobile band of 250MHz.In 1980, the UK launched a digital paging system on the 150MHz mobile frequency band.
On September 16, 1983, Shanghai, China launched an analog paging system on the 150MHz mobile band.On May 1, 1984, Guangzhou launched the digital paging system on the 150MHz mobile frequency band.On November 15, 1991, Shanghai launched the Chinese character paging system on the 150 MHz mobile frequency band.By the end of 1991, China had opened 426 paging systems and 877000 pagers.
working principle
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The paging receiver is small in appearance, but it is a radio receiver with all five internal features. Its working principle is the same as that of an ordinary radio station, and it is generally composed of two parts: the radio frequency receiving unit and the logic control unit.The RF receiving unit is composed of antenna, high level amplifier, mixer, intermediate amplifier and filter, amplitude limiting amplifier, frequency discrimination and other circuits.The logic control unit is composed of microprocessor, decoder, integrated function interface module, address and function data memory, LCD and boost circuit.It is generally required to be small in size, low in power consumption, high in reliability, easy to carry, and with good dust-proof, shockproof and impact resistance.In addition to audio pagers, there are digital display pagers and Chinese character display pagers on the market.At present, China's wireless paging has developed from the local paging network to the regional paging network, and gradually formed the national paging network.
component
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A simple paging system consists of three parts: paging center, base station and paging receiver.If the calling user wants to find a called user, he can use the local telephone to dial the paging station, and inform the called user of the paging number, the name of the calling user, the call back number, and the brief information content.The operator inputs it into the computer terminal, codes it and sends it out by the base station radio transmitter.If the called user is within its coverage range, his paging receiver will receive the wireless paging signal and emit beeping sound or vibration.At the same time, the received information is stored in the memory and displayed on the LCD.At this time, the called user can get the information transmitted, or call the calling user back.This is the case where the call center is controlled manually.If the call center is automatically controlled, the whole process is carried out by the computer in the paging center.In China, the radio paging frequency is specified as 160MHz, 450MHz and 900MHz, but the actual frequency is mostly 160MHz.
Networking mode
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The networking mode of wireless paging can be divided into local paging network, regional paging network and national paging network.The local paging network covers a long-distance number area.The local paging network can adopt single zone or multi zone system. There is only one base station transmitting area in the service area of single zone system, that is, the paging center only has one base station.The coverage of a single base station depends on the height of the transmitting antenna, the propagation environment and the effective radiation power.For example, the height of the transmitting antenna is 50m, the effective radiation power is 100W, the outdoor coverage in urban areas is 15km, and the indoor coverage is about 5km. In rural areas, the outdoor half length is about 25km, and the indoor coverage is about 8km.When it is required to expand the service scope, the multi zone system can be used, that is, one paging center has multiple base stations, and each base station is connected to the paging center with a dedicated trunk circuit for the industrial line.The BTSs work at the same time, that is, they send the same signal at the same time, so they need to be synchronized.In the multi zone system, in order to avoid the phase difference of signals from different base stations in the overlap area, it is necessary to carry out equalization. At the same time, in order to avoid beat interference, it is necessary to use frequency offset technology.The paging signal sent by the paging station shall be coded in a certain coding format.At present, POCSAG code is mostly used.
Structure of wireless paging network
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It is divided into local wireless paging network structure and regional wireless paging network structure.
The local wireless paging network structure consists of the local telephone network and the local wireless paging system.The radio paging system can be divided into single base station system and multi base station system.The structure of multi base station local wireless paging network is shown in Figure 1.
Figure 1 Structure Diagram of Multi base Station Local Radio Paging Network
The wireless paging system includes a base station and several peripheral base stations, data circuits, paging terminals (manual or automatic) and pagers.The whole paging service area is divided into several wireless areas, and one base station or peripheral base station is set in each area.The base station and peripheral base stations are connected to the paging terminal through the data circuit.The paging terminal is connected to the local telephone network via trunk line.The single base station radio paging network has only one base station, no peripheral base stations, and other parts are the same as the multi base station radio paging network (see page 20 of the color image insert page).
The paging terminal processes the called user number and the calling user message sent from the local telephone network in a centralized manner to realize the functions of repeated calls, multiple station query, recording, statistics and billing, and then codes them.The encoded digital signal is transmitted to the base station and peripheral base stations through the data circuit, and transmitted simultaneously by the transmitters of each base station (including peripheral base stations).The called pager receives the signal transmitted by the base station and generates audio and information display at the same time.
The structure of regional wireless paging network is shown in Figure 2.The local telephone network is connected to local paging terminals through trunk lines. Several local paging terminals are connected to the regional control center through special data circuits. The regional control center is connected to several base stations and peripheral base stations in the local paging coverage area through special data circuits.
The local paging terminal processes the called user number and the calling user message sent from the local telephone network in a centralized manner to realize the functions of repeated calls, multiple station inquiry, recording, statistics and billing, and then converts them into ASCII code.This code is transmitted to the regional control center through the special data circuit.The regional control center collects the information from each local paging terminal and codes it.The encoded digital signals are transmitted to the base stations and peripheral base stations in each local paging coverage area through special data circuits, and are transmitted simultaneously by all base station (including peripheral base stations) transmitters.After receiving the signal transmitted from the base station, the called pager generates audio and information display at the same time.
Figure 2 Schematic Diagram of Regional Radio Paging Network Structure
Queuing machines are used to queue incoming calls from multiple relays, which can balance traffic allocation.
