What is a network cat?

Network cat refers to modem (modem). A modem is a device that converts "digital signals" and "analog signals" into each other; it converts digital signals into analog signals through modulation at the transmitting end, and then converts analog signals into digital signals through demodulation at the receiving end. A modem translates a computer's digital signals into analog signals that can be sent along an ordinary telephone line. These analog signals can then be received by another modem at the other end of the line and translated into a language that the computer can understand.

The operating environment of this tutorial: Windows 7 system, Dell G3 computer.

Network modem refers to a modem (modem), which is used to connect a computer to a broadband. Only with it can the computer enter a normal state of Internet access.

modem (modem)

Modem, commonly known as "cat", is a kind of computer hardware; its main function is to carry out "digital signals" and conversion between "analog signals".

It can translate the computer's digital signals into analog signals that can be transmitted along ordinary telephone lines, and these analog signals can be received by another modem at the other end of the line and translated into a language that the computer can understand.

The information in the computer is a digital signal composed of "0" and "1", but what is transmitted on the telephone line can only be an analog electrical signal. Therefore, when two computers want to transmit data through a telephone line, a device is needed to perform digital-to-analog conversion. This is why you need to use a modem when dialing up the Internet through a telephone line (ADSL).

Modem is actually the abbreviation of Modulator and Demodulator. It is a method of modulating the digital signal to be transmitted onto the carrier wave or separating the digital signal from the carrier wave.

The so-called modulation is to convert digital signals into analog signals transmitted on telephone lines; demodulation is to convert analog signals into digital signals, collectively called a modem. It converts digital signals into analog signals through modulation at the transmitting end, and then converts analog signals into digital signals through demodulation at the receiving end.

When the computer sends data, the Modem first converts the digital signal into the corresponding analog signal. This process is called "modulation". Before the modulated signal is transmitted to another computer through the telephone carrier, the receiver's Modem is responsible for restoring the analog signal to a digital signal that the computer can recognize. This process is called "demodulation." It is through such a digital-to-analog conversion process of "modulation" and "demodulation" that remote communication between two computers is achieved.

It is mainly used for data communication in telephone networks and plays an important role in network interconnection and remote access.

The current modem is very mature in terms of adaptive, data compression and network coding modulation technology. The data transmission of each voice channel can be as high as 56kbps, which is basically close to the theoretical maximum rate of telephone lines.

According to the modem form and installation method, it can be roughly divided into the following four categories:

1. External Modem

External Modem placement Outside the chassis, it is connected to the host through the serial communication port. This modem is convenient, smart and easy to install, and the flashing indicator light makes it easy to monitor the working status of the modem. However, external Modem requires additional power supply and cables.

2. Built-in Modem

Built-in Modem needs to disassemble the chassis during installation, and the interrupt and COM port must be set, so the installation is more cumbersome. This kind of Modem occupies the expansion slot on the motherboard, but does not require additional power supplies and cables, and is cheaper than external Modem.

3. PCMCIA plug-in modem

Plug-in modem is mainly used in notebook computers and is compact in size. Together with a mobile phone, mobile office can be easily realized.

4. Rack-mounted Modem

Rack-mounted Modem is equivalent to a group of Modems concentrated in a box or shell and powered by a unified power supply. Rack-mounted Modem is mainly used in central computer rooms of Internet/Intranet, telecommunications bureaus, campus networks, financial institutions and other networks.

In addition to the above four common Modems, there are now ISDN modems and a modem called CableModem, and there is also an ADSL modem. CableModem uses cable TV cables for signal transmission. It not only has modem and demodulation functions, but also integrates routers, hubs, and bridges. The theoretical transmission speed can reach more than 10Mbps. Through CableModem access to the Internet, each user has an independent IP address, which is equivalent to having a personal dedicated line.

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