Pageer (the one that beeps), why not just use your mobile phone to send text messages?

Wireless paging is a one-way personal selective calling system that transmits call signals to mobile users carrying pagers. The pager is lightweight and easy to carry and use. At present, wireless paging has developed greatly in our country, and the number of users has reached millions. A simple paging system consists of 3 parts: paging center, base station and paging receiver. If the calling user wants to find a called user, he can use a local phone to call the paging station and inform the called user of the paging number, the name of the calling user, the callback number and the brief message content. The operator inputs it into the computer terminal, is encoded and finally sent out by the base station radio transmitter. If the called user is within its coverage, the paging receiver on him will receive the wireless paging signal and make a beep or vibrate. At the same time, the received information is stored in the memory and displayed on the LCD screen. At this time, the called user can obtain the transmitted information, or return a call to the calling user for contact. This is where the call center is controlled by humans. If the call center is under automatic control, the entire process is performed by the computer in the paging center. In my country, the frequencies for wireless paging are stipulated as 160MHz, 450MHz, and 900MHz frequency bands, but the actual frequency band used is mostly 160MHz. Wireless paging networking methods can be divided into local paging network, regional paging network and national paging network. The local paging network is the coverage area of ??a long distance numbering area. The local paging network can adopt a single-area or multi-area system. There is only one base station transmission area in the service area of ??the single-area 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 range in urban areas is 15km, and the indoor coverage range is about 5km. In rural areas, the outdoor coverage range is about 25km, and the indoor coverage range is about 8km. When it is required to expand the service scope, a multi-zone system can be adopted, that is, one paging center has multiple base stations, and each base station is connected to the paging center through a dedicated relay circuit for the work line. Each base station works simultaneously, that is, it sends the same signal at the same time, so it needs to be synchronized. In a multi-region system, in order to avoid phase differences in the arrival of signals from different base stations in overlapping areas, equalization is required. At the same time, in order to avoid beat interference, frequency offset technology needs to be used. The paging signal sent by the paging station should be encoded and adopt a certain encoding format. Currently, POCSAG codes are mostly used. The paging receiver has a small appearance, but inside it is a complete radio receiver. Its working principle is the same as that of an ordinary radio station. It is generally composed of two parts: a radio frequency receiving unit and a logic control unit. The radio frequency receiving unit is composed of antenna, high amplifier, mixing, medium amplifier and filtering, limiting amplification and frequency discrimination circuits. The logic control unit consists of a microprocessor, a decoder, a comprehensive functional interface component, an address and functional data memory, a liquid crystal display and a boost circuit. Generally required are small size, low power consumption, high reliability, easy to carry, and have good dustproof, shockproof and impact resistance properties. In addition to audio pagers, there are also digital display pagers and Chinese character display pagers on the market. Now our country's wireless paging has developed from local paging network to regional paging network, and gradually formed a national paging network.