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 KVM Switches, Industrial Computer,Industrial Notebook Manufacturer in China |
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What is Modem?
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"Modem" is an acronym that stands for "Modulator Demodulator". These are the technical terms for the way it modulates outgoing digital signals from a computer or other digital device to analog signals for a conventional copper twisted pair telephone line and demodulates the incoming analog signal and converts it to a digital signal for the digital device. A modem allows you to send and receive information over the phone line with your computer. You could send a picture of your dog to a friend, or receive (download) a document sent to you via email.
There is one standard interface for connecting external modems to computers. Consequently, any external modem can be attached to any computer that has an port, which almost all personal computers have. There are also modems that come as an expansion board that you can insert into a vacant expansion slot. These are sometimes called onboard or internal modems. Most modems have built-in support for the more common protocols -- at slow data transmission speeds at least, most modems can communicate with each other. At high transmission speeds, however, the protocols are less standardized.
The designation asymmetric simply means that the modem is faster at downloading (getting data), than uploading (sending data). The ADSL modem has significant, immediate advantages over the dial-up modem.
In recent years, the 2400 bits per second modem that could carry e-mail has become obsolete. 14.4 Kbps and 28.8 Kbps modems were temporary landing places on the way to the much higher bandwidth devices and carriers of tomorrow.
The ADSL modem can accommodate a telephone conversation because of available bandwidth on the dedicated copper wire, which runs from households and businesses to the telephone company (Telco). A parallel can be made to a multi-lane freeway with several lanes open for additional traffic. The ADSL modem uses the additional lanes (higher frequencies) without interfering with existing voice traffic. An ADSL modem requires ADSL service through an Internet Service Provider (ISP). This type of modem will not work with a dial-up account.
With Digital Subscriber Line (DSL) systems, now being deployed in a number of communities, bandwidth on twisted-pair can be in the megabit range.
Yet another type of modem uses cable TV wiring rather then the phone line to provide Internet connectivity. A cable modem requires service from a cable TV provider for Internet connectivity.
Computers use modems to communicate with one another over a network.
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