Modem

Modem, is a kind of computer hardware, it can remove the computer digital signal can be translated into ordinary telephone line along the pulse signal transmission, and the pulse signal and can be lines on the other side of another modems receiving, and translated into computer can understand the language. This simple process completed the communications between the two computers.

Modem, is actually Modulator (Modulator) and Demodulator (Modem) abbreviation. So-called modulation, is to convert digital signal wire transmission of analog signals, Demodulation, namely the analog signal converted into digital signals. The company modems.

MODEM English is of a MODEM and its role is to analogue and digital signals "interpreters". Electronic signal is divided into two kinds, one kind is "analog signals", a kind of "digital signal". We use the telephone wires is analog signals, and PC transmitted between digital signals. So when you want to put his own computer through telephone lines connected to the Internet, you must use modems to "translate" two different signals. Connected to the Internet, when a PC to Internet send the message, because the telephone transmission is analog signals, thus must use modems to the digital signal "translation" into analog signals, can teleport to Internet, this process is called "modulation". When the PC to obtain information from Internet, because through telephone lines from Internet coming from information is analog signal, so PCS

Want to read them, also must have the aid of modem this "translation", this process is called "demodulation." Generally called "demodulation."

history

Modem is for beginning in the 1950s semi-automatic ground anti-air multiple-security system (SEGE) development, used to connect different base of terminals, radar station and command control center to the United States and Canada SAGE command center. SAGE operation in private sidings road, but at both ends of the equipment with today's use of Modem root is not the same thing. IBM is SAGE system in computer and Modem suppliers. After several years of Airlines as chief executive officer (CEO) and IBM a regional manager a meeting prompted "mini - SAGE" this kind of aviation automatic ticket system. In this system, a ticket center is located in the terminal connections in central computer, used to manage ticket validity and time. This system, called Sabre, it is today the early prototypes Sabre system.

In the early 1960s, commercial application of computer grew in popularity, and the above technical achievements, 1962, AT&T released the first commercially modem, Bell 103. Usage two tones said of 1s and 0s frequency shift keying technology, 103, have been able to achieve 300 bit/s transmission speed. A short time later versions Bell 212 is developed and transferred into more stable YiXiang keying technology the data rate increase to 12 bit/s. The system USES similar Bell 201 two-way signals in 4 to private sidings integrating way realized 2,400 bit/s.

No intelligent Modem is a significant progress, 1981 no communication developed successfully. Intelligent Modem is a simple 300bpsModem, using a standard, the built-in Bell103 signaling a small controller, can let computer sending commands to control telephone lines, such as off-hook, dial, heavy dial, hang machine etc. Function.

In intelligent Modem before, almost all the Modem all need two steps to produce a link: the first step, artificially in telephone call their number, then put the receiver on acoustic coupler in Modem incidental, with an composed of two rubber cup in voice signal and electrical signals used to convert between equipment. Using intelligent acoustic coupler Modem wouldn't need, but directly connected in Modem standard telephone lines or socket. Then computers can be automatically complete connect to talk on the phone and call number function. This change greatly simplified bulletin board by telephone under 0120-2714540 (BBS) of the installation and use.

The 1980s Modem rate has not changed much. The average U.S. use a bell 212 similar with 24 bit/s system, and the European system a slightly different. By the late 1980s most Modem can support when all the standard, 2400bit/s grew in popularity. Large specific use standard also filled in, usually using high-speed channel accept low-speed channel to send, a typical example is France's Minitel system, user terminals spend most of the time in receiving information. Minitel terminal with Modem 1200bit/s accepts data 75 bit/s send command feedback to the server.

use

In the computer information is by "0" and "1" composed of digital signal, and in telephone wire transfer of but is only analog signals. Thus, when two computers to through telephone wires for data transmission, it need a device responsible for analog-to-digital conversion. The digital-to-analog converters is of a Modem. Computer in sending data, first by the Modem converts digital signals are converted to corresponding simulation signal, the process is called "modulation". After the modulated signals through phone carrier transferred to another computer via before, also want to recipient Modem undertakes the analog signal reduction for the computer can identify the digital signal, the process is called "demodulation". It is through such a "modulation" and "demodulation" analog-to-digital conversion process so as to realize the remote communication between two computers.

category

Generally speaking, according to Modem forms and installation, can can be divided into the following four categories:

External type of a Modem

External extended Modem placed on chassis outside, through serial communication mouth and host connection. This kind of Modem convenient, easy installation, flashing dexterous facilitate the indicator of the working conditions of the monitoring of a Modem. But the external extended Modem need to use additional power and cables.

Built-in Modem

Built-in Modem when installation needs, and to open box interrupt and the COM setting, installation is relatively complicated. This kind of Modem takes on the mainboard of expansion slot, but no extra power and cable, and the price is external extended Modem to cheaper.

PCMCIA plug-in of a Modem

Plug-in Modem is mainly used for laptops, volume dainty. Cooperate with mobile phones, can easily make mobile office.

Rack-mountable of a Modem

Rack-mountable Modem equivalent a group of Modem focuses on a box or covering, and by a unified power supply. Rack-mountable Modem is mainly used in Internet/Intranet, telecommunication bureau, campus network, financial institutions and other network of computer and network center.

In addition to the above four common Modem outside, now have the ISDN modems and called a Cable Modem modems, another is ADSL modems. Cable Modem through the Cable TV Cable signals, not only have demodulation functions, but also set a router, hubs, a bridge at a suit, theoretical transmission speed can reach more 10Mbps above. Through the Cable Modem online, each user has a separate IP address, equivalent to have a personal line. At present, shenzhen cable television tianwei network company has launched this based on the Internet access service cable television, access rate for 2Mbps - 10Mbps!

USB modem

USB technology, the emergence of computer peripheral devices provide faster and more simple method of connecting the SHARK company takes the lead, launched the USB interface of 56K modem, this only pager size of modem truly for the traditional serial modems brings its own challenges. Just put it up in host to the USB interface can, usually hosts have 2 USB interface, and USB interface can connect 127 devices, if you want to connect more equipment can also buy USB hubs. Usually USB monitor, printer able to serve as a USB hubs, because they have in addition to connect hosts the USB interface outside also provide 1-2 USB interface.

Transfer mode

Modem was originally used for data transmission. However, as the user demand is growing and the fierce competition between manufacturers, on the market at present more and more appeared some "two-in-one", "three-in-one" of a Modem. These Modem besides can for data transmission outside, still have fax and voice transmission function.

1, Fax mode (tlx.number Modem)

Through Modem on fax, in addition to save a dedicated fax fees, benefits and many: can directly put inside a computer file fax the other party of the computer or fax machine, without first put the documents printed, Can docking received your fax convenient to store or editing, Can overcome the common fax machine caused by using thermal papers and cause the handwriting subside problem; Because of a Modem used error correction technology, fax quality is better than ordinary fax machine, especially for graphic fax is even more so. The current tlx.number Modem mostly follow vladimir 29 and v. 17 Fax protocol. One v. 29 support 9600bps fax rate, and v. 17 May support 14400bps fax rate.

2, speech mode (Voice of a Modem)

Speech pattern mainly provides telephone recording message and full-duplex hands-free conversations function, make telephone and computer as a whole. Here, mainly is a new Voice transmission mode - Digital Voice and Simultaneous DSVD (Data). DSVD is by Rockwell, Hayes,

U.S.R obotics, Intel and other companies in 1995 raises an voice transmission standards, is the existing v. 42 error correction agreement the expansion. By using DSVD Digi Talk of digital voice and data with preach technology, enable the Modem can in ordinary telephone line on one side of the data transmission of one side of the phone.

DSVD Modem retained 8K bandwidth (also some Modem retain 8.5 K) for pronunciation transmission bandwidth, the rest of the bandwidth is used in data transmission. Speech in a transmission before will be the first to compress and then required to transmit data comprehensive together, through phone carrier transmission to each other users. In the receiver, Modem first voice and data separated, and then the speech signal with decompression and/mode conversion, thus realize data/speech of simultaneous interpreters. DSVD in Modem distance education, collaborative work, network game has broad prospect of application. But at present, because of the DSVD Modem than common Voice of a Modem to expensive, and to realize data/speech with preach function, need to use the other side also DSVD Modem, which, to a certain extent, hampered in DSVD Modem popularization.

Modem, is a kind of computer hardware, it can remove the computer digital signal can be translated into ordinary telephone line along the pulse signal transmission, and the pulse signal and can be lines on the other side of another modems receiving, and translated into computer can understand the language. This simple process completed the communications between the two computers.Modem, is actually Modulator (Modulator) and Demodulator (Modem) abbreviation. So-called modulation, is to convert digital signal wire transmission of analog signals, Demodulation, namely the analog signal converted into digital signals. The company modems.MODEM English is of a MODEM and its role is to analogue and digital signals "interpreters". Electronic signal is divided into two kinds, one kind is "analog signals", a kind of "digital signal". We use the telephone wires is analog signals, and PC transmitted between digital signals. So when you want to put his own computer through telephone lines connected to the Internet, you must use modems to "translate" two different signals. Connected to the Internet, when a PC to Internet send the message, because the telephone transmission is analog signals, thus must use modems to the digital signal "translation" into analog signals, can teleport to Internet, this process is called "modulation". When the PC to obtain information from Internet, because through telephone lines from Internet coming from information is analog signal, so PCSWant to read them, also must have the aid of modem this "translation", this process is called "demodulation." Generally called "demodulation."historyModem is for beginning in the 1950s semi-automatic ground anti-air multiple-security system (SEGE) development, used to connect different base of terminals, radar station and command control center to the United States and Canada SAGE command center. SAGE operation in private sidings road, but at both ends of the equipment with today's use of Modem root is not the same thing. IBM is SAGE system in computer and Modem suppliers. After several years of Airlines as chief executive officer (CEO) and IBM a regional manager a meeting prompted "mini - SAGE" this kind of aviation automatic ticket system. In this system, a ticket center is located in the terminal connections in central computer, used to manage ticket validity and time. This system, called Sabre, it is today the early prototypes Sabre system.In the early 1960s, commercial application of computer grew in popularity, and the above technical achievements, 1962, AT&T released the first commercially modem, Bell 103. Usage two tones said of 1s and 0s frequency shift keying technology, 103, have been able to achieve 300 bit/s transmission speed. A short time later versions Bell 212 is developed and transferred into more stable YiXiang keying technology the data rate increase to 12 bit/s. The system USES similar Bell 201 two-way signals in 4 to private sidings integrating way realized 2,400 bit/s.No intelligent Modem is a significant progress, 1981 no communication developed successfully. Intelligent Modem is a simple 300bpsModem, using a standard, the built-in Bell103 signaling a small controller, can let computer sending commands to control telephone lines, such as off-hook, dial, heavy dial, hang machine etc. Function.In intelligent Modem before, almost all the Modem all need two steps to produce a link: the first step, artificially in telephone call their number, then put the receiver on acoustic coupler in Modem incidental, with an composed of two rubber cup in voice signal and electrical signals used to convert between equipment. Using intelligent acoustic coupler Modem wouldn't need, but directly connected in Modem standard telephone lines or socket. Then computers can be automatically complete connect to talk on the phone and call number function. This change greatly simplified bulletin board by telephone under 0120-2714540 (BBS) of the installation and use.The 1980s Modem rate has not changed much. The average U.S. use a bell 212 similar with 24 bit/s system, and the European system a slightly different. By the late 1980s most Modem can support when all the standard, 2400bit/s grew in popularity. Large specific use standard also filled in, usually using high-speed channel accept low-speed channel to send, a typical example is France's Minitel system, user terminals spend most of the time in receiving information. Minitel terminal with Modem 1200bit/s accepts data 75 bit/s send command feedback to the server.useIn the computer information is by "0" and "1" composed of digital signal, and in telephone wire transfer of but is only analog signals. Thus, when two computers to through telephone wires for data transmission, it need a device responsible for analog-to-digital conversion. The digital-to-analog converters is of a Modem. Computer in sending data, first by the Modem converts digital signals are converted to corresponding simulation signal, the process is called "modulation". After the modulated signals through phone carrier transferred to another computer via before, also want to recipient Modem undertakes the analog signal reduction for the computer can identify the digital signal, the process is called "demodulation". It is through such a "modulation" and "demodulation" analog-to-digital conversion process so as to realize the remote communication between two computers.categoryGenerally speaking, according to Modem forms and installation, can can be divided into the following four categories:External type of a ModemExternal extended Modem placed on chassis outside, through serial communication mouth and host connection. This kind of Modem convenient, easy installation, flashing dexterous facilitate the indicator of the working conditions of the monitoring of a Modem. But the external extended Modem need to use additional power and cables.Built-in ModemBuilt-in Modem when installation needs, and to open box interrupt and the COM setting, installation is relatively complicated. This kind of Modem takes on the mainboard of expansion slot, but no extra power and cable, and the price is external extended Modem to cheaper.PCMCIA plug-in of a ModemPlug-in Modem is mainly used for laptops, volume dainty. Cooperate with mobile phones, can easily make mobile office.Rack-mountable of a ModemRack-mountable Modem equivalent a group of Modem focuses on a box or covering, and by a unified power supply. Rack-mountable Modem is mainly used in Internet/Intranet, telecommunication bureau, campus network, financial institutions and other network of computer and network center.In addition to the above four common Modem outside, now have the ISDN modems and called a Cable Modem modems, another is ADSL modems. Cable Modem through the Cable TV Cable signals, not only have demodulation functions, but also set a router, hubs, a bridge at a suit, theoretical transmission speed can reach more 10Mbps above. Through the Cable Modem online, each user has a separate IP address, equivalent to have a personal line. At present, shenzhen cable television tianwei network company has launched this based on the Internet access service cable television, access rate for 2Mbps - 10Mbps!USB modemUSB technology, the emergence of computer peripheral devices provide faster and more simple method of connecting the SHARK company takes the lead, launched the USB interface of 56K modem, this only pager size of modem truly for the traditional serial modems brings its own challenges. Just put it up in host to the USB interface can, usually hosts have 2 USB interface, and USB interface can connect 127 devices, if you want to connect more equipment can also buy USB hubs. Usually USB monitor, printer able to serve as a USB hubs, because they have in addition to connect hosts the USB interface outside also provide 1-2 USB interface.Transfer modeModem was originally used for data transmission. However, as the user demand is growing and the fierce competition between manufacturers, on the market at present more and more appeared some "two-in-one", "three-in-one" of a Modem. These Modem besides can for data transmission outside, still have fax and voice transmission function.1, Fax mode (tlx.number Modem)Through Modem on fax, in addition to save a dedicated fax fees, benefits and many: can directly put inside a computer file fax the other party of the computer or fax machine, without first put the documents printed, Can docking received your fax convenient to store or editing, Can overcome the common fax machine caused by using thermal papers and cause the handwriting subside problem; Because of a Modem used error correction technology, fax quality is better than ordinary fax machine, especially for graphic fax is even more so. The current tlx.number Modem mostly follow vladimir 29 and v. 17 Fax protocol. One v. 29 support 9600bps fax rate, and v. 17 May support 14400bps fax rate.2, speech mode (Voice of a Modem)Speech pattern mainly provides telephone recording message and full-duplex hands-free conversations function, make telephone and computer as a whole. Here, mainly is a new Voice transmission mode - Digital Voice and Simultaneous DSVD (Data). DSVD is by Rockwell, Hayes,U.S.R obotics, Intel and other companies in 1995 raises an voice transmission standards, is the existing v. 42 error correction agreement the expansion. By using DSVD Digi Talk of digital voice and data with preach technology, enable the Modem can in ordinary telephone line on one side of the data transmission of one side of the phone.DSVD Modem retained 8K bandwidth (also some Modem retain 8.5 K) for pronunciation transmission bandwidth, the rest of the bandwidth is used in data transmission. Speech in a transmission before will be the first to compress and then required to transmit data comprehensive together, through phone carrier transmission to each other users. In the receiver, Modem first voice and data separated, and then the speech signal with decompression and/mode conversion, thus realize data/speech of simultaneous interpreters. DSVD in Modem distance education, collaborative work, network game has broad prospect of application. But at present, because of the DSVD Modem than common Voice of a Modem to expensive, and to realize data/speech with preach function, need to use the other side also DSVD Modem, which, to a certain extent, hampered in DSVD Modem popularization.