What does modem mean? What does a modem look like

turn) modem (tiáozhìjiětiáoqì) i.e. modem

It can convert digital signals into analog signals and transmit them on the network, and can also convert the received analog signals into digital signals. Since most personal computers are connected to the computer network through the public ** network, the above conversion needs to be carried out through a modem.

It is a device for signal conversion between the computer and the first line, which is composed of two parts, a modulator and a demodulator, the modulator is a device that modulates the digital signal of the computer (such as files, etc.) into a sound signal that can be transmitted on the first line, and at the receiving end, the demodulator converts the sound signal into a digital signal that the computer can receive. Data communication between computers can be realized through a modem and a ** line.

At present, there are two main types of modems: built-in and external.

The built-in modem is actually a computer's expansion card, which can be used by plugging into an expansion slot in the computer, and it does not occupy the computer's serial port. Its connection is quite simple, insert the ** cable connector into the "line" socket on the card, and the other interface "phone" on the card is connected to the ** machine, when the modem is not used at all, the ** machine is not affected at all.

The external modem is a cassette device placed outside the computer, it needs to occupy a serial port of the computer, and it also needs to be connected to a separate power supply to work, there are several status indicators on the external modem panel, which can be convenient for you to monitor the communication status of the modem, and the external modem is easy to install and disassemble, easy to set up and maintain, and easy to carry. The connection of the external modem is also very convenient, and the connection of the phone and line is the same as that of the built-in modem. However, an external modem must use a serial cable to connect one of the serial ports of the computer to the serial port of the modem, and this serial cable is usually shipped with the external modem.

An important performance parameter of the modem is the transmission rate, which is currently available in both 56k modems on the market, and 56k modems have become the mainstream products in the market. However, due to the limitation of domestic communication lines, as well as the fact that there are too many users and too few international exports, it is difficult to achieve the above rates in normal use, so if the transmission rate is only a few kilobytes per second or even lower when you use it, you don't need to wonder if there is something wrong with your computer or modem.

The main function of the modem is to convert the analog signal of ** into a digital signal for the computer, and its bandwidth is:

2m，4m，6m

Modems often look like small, black, elongated square boxes. Typically, they have two to four antennas, but not every modem includes an external antenna.

Modem is an abbreviation of "modulator" and "demodulator", affectionately called "cat" according to the homonym of modem. It is a device that converts a digital signal into an analog signal through modulation at the transmitter end and then converts the analog signal into a digital signal through demodulation at the receiving end.

How does the modem work:

The information in the computer is composed of digital signals composed of "0" and "1", while the transmission on the ** line can only be analog electrical signals. If no measures are taken to use analog channels to transmit digital signals, there will inevitably be great errors (distortions), so to transmit data on an ordinary network, it is necessary to convert the digital signal into the audio spectrum required by the original design of the network (i.e., 300Hz 3400Hz).

Modulation is to use baseband pulses to control a certain parameter of the carrier waveform to form a signal suitable for line transmission.

Demodulation means that when the modulated signal reaches the receiving end, the analog signal converted by the modulator removes the carrier and returns to the original baseband digital signal.

The use of a modem can also convert audio signals to higher frequency signals and higher frequency signals to audio signals. Therefore, another purpose of modulation is to facilitate the reuse of lines, so as to improve the utilization rate of lines.

Regarding the meaning of modem, the calculation is explained by the technical terms of the machine.

Modem (Offers two functions. One is to convert the synchronous multiplex output data bit stream from the "multiplex decomposition" module into an analog signal that can be transmitted on the PSTN network; Another function is to convert the received analog signal into a synchronous data bit stream, and then send it to the "multiplex multiplex decomposition" (for decomposition. "Modem Control (TER)" is used for the communication process of the auto-answering device and the auto-call device, where TER represents the third version.

It is a protocol that lately initiates the data transfer session process in the PSTN network.

Introduction to Modulators:

The modem is composed of two parts, the modulator and the demodulator, wherein the modulator modulates the data information into a signal suitable for transmission channel transmission, and the demodulator demodulates and restores the received signal into data information, and the modem belongs to the data circuit equipment DCE in the data communication equipment.

Modulation is to use the baseband pulse to control a certain parameter of the carrier waveform to form a signal suitable for line transmission, demodulation is when the modulated signal arrives at the receiving end, the analog signal converted by the modulator removes the carrier and restores it to the original baseband digital signal, and the modem can also convert the audio signal into a higher frequency signal and the higher frequency signal into an audio signal, so another purpose of modulation is to facilitate line reuse, so as to improve line utilization.

The role of the modulator:

The data signal emitted by the signal source can be successfully converted into an analog signal suitable for analog signal transmission, and at one end of the data, it will complete the conversion in the opposite direction of the signal source, and can also deal with the noise and distortion waveform.

When the data is being transmitted, the information will continue to be synchronized at the receiving end, it will extract the synchronous information sent and have a genlock, and then use the carrier that is in phase with the source for sampling and the source to generate time, so as to ensure the synchronization of the message and the source.

The hard disk can also take advantage of the orthogonality of the seat number to realize channel multiplexing by using various coding and modulation methods. At the same time, it can also compensate for the interference damage of harmful factors to the signal.