A modem is a computer hardware that translates digital signals from a computer into analog signals that can be transmitted along a regular telephone line, which can be received by another modem on the other side of the line and translated into a language that is readable by the computer. This simple process completes the communication between two computers.
The modem is the abbreviation of the Modulator (modulator) and the Demodulator (demodulator), which is called the modem (the RTHK is called the Data Machine), which is called "cat" according to the homophonic of modem. It is a device that converts the digital signal to analog signal through modulation at the transmitter, and then the analog signal is converted to digital signal through demodulation at the receiver.
The so-called modulation is to convert the digital signal into the analog signal transmitted on the telephone line; demodulation, the analog signal is converted to digital signal. Collectively known as modems.
The modem English is modem, its function is analog signal and digital signal "translator". The electronic signal is divided into two kinds, one is "analog signal", one is "digital signal". The telephone lines we use are analog signals, and the digital signals are transmitted between PCs. So when you want to connect your computer to the Internet through a telephone line, you must use a modem to "translate" two different signals. When connected to the Internet, when the PC sends information to the Internet, because the telephone line transmits analog signal, it is necessary to use a modem to "translate" the digital signal into analog signal to transmit to the Internet, this process is called "modulation". When the PC obtains information from the Internet, because the information transmitted from the Internet through the telephone line is analog signal, so PC want to understand them, also must use the modem this "translation", this process is called "demodulation." In general, it is called "modulation and Demodulation".