What is a Modem?

What is a Modem?
babyyum321Asked:
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rbrCommented:
A modem is an interface (hard or software) which transfers seriell data from a digital level to an analog level.
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rayt333Commented:
Acronym for modulator-demodulator. A modem is a device or program that enables a computer to transmit data over telephone lines. Computer information is stored digitally, whereas information transmitted over telephone lines is transmitted in the form of analog waves. A modem converts between these two forms.

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vikiingCommented:
>>A modem is a device or program

A modem is a device, not a program, 'cause it's a hardware component.

Beside that, the principle of worki relies on the fact that a certain sound (the carrier) can be modulated, tha same way a boradcasting station does: the main frequency (carrier) is modulated by another signal (the human voice, in the case of the broadcasting station; or a square wave, in the case of a digital bit). That's the "modulating" phase.

The so-obtained compound signal is then sent thru the medium (the air [radio] or the telephone wires [the computer]). After reaching the other end, the "demodulating" phase negis: the "enveloping signal" is removed from the composed signal, leaving the original information intact.

All that is needed because telephone wires are unable to transmit digital signs (there are some electrical characteristics which make copper wires totally useless for binary transmitting process).
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craig_capelCommented:
to an extent, you can have all the work done by the CPU for example Zoltrix modems use software, the hardware of the card is simply to allow you to plug a line in to it....
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vikiingCommented:
>>the hardware of the card is simply to allow you to plug a line in to it

Not always; there are Zoltrix modem which have a firmware (like any other hard-modem) that perform quite much more than simply "to allow to plug a line".

Data compression, error checking, parity, signals control, command interpreting, auto testing, CRC, and a lot of more things put a modem in a level quite higher than a "dumb device".
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craig_capelCommented:
ok, unlike other modems, you have to agree that the main part is the cpu, you cant use a zoltrix on anything less than an MMX cpu
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vikiingCommented:
Friend Craig: during years, I've used a Zoltrix modem on a 386 machine...
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rbrCommented:
The only real hardware you need is an A/D and a D/A converter. All other things can be made by software.
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1cellCommented:
<A modem is a device, not a program, 'cause it's a hardware component. >>

most modems these days are actually software based modems.  Unlike the past few years' modems, the manufacturers these days are saving a few pennies by removing the technology from the modem and putting the burden of A/D and D/A conversion on the processor.  Basically, these modems ( winmodems, hfc modems, software modems ) are just a way to get the phone line into the computer and get the data to the processor.  The processor, in turn, uses the modem's software to translate the data and then convert it.  Of course, this process slows the system and internet connection though mosdt manufacturers are putting out systems with processors fast enough to handle the load.

The bottom line is, as was mentioned many times above, a modem is a device used to convert digital to analog and vice versa.  Different modems do it different ways but it's all the same result.  
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ran1Commented:
A better answer.

http://www.pctechguide.com/17scomms.htm#Modems

Details on how a modem works including illustrations.
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