Modem name and function?
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Modem name and function?

 
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species8350
Guest
Posted: Sun Oct 30, 2005 5:41 pm    Post subject: Modem name and function? Reply with quote
A modem takes an analog signal and converts it to a digital signal, and
vice versa. So a modem is an analog to digital converter. So why is it
called a modem (modulator/demodulator)?

Thanks
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Ken
Guest
Posted: Sun Oct 30, 2005 7:36 pm    Post subject: Re: Modem name and function? Reply with quote
species8350 wrote:
Quote:
A modem takes an analog signal and converts it to a digital signal, and
vice versa. So a modem is an analog to digital converter. So why is it
called a modem (modulator/demodulator)?

Thanks


I believe the process of converting a signal from one format (digital
in this case) and converting it to another (a serial signal of varying
frequency) is called modulation. Therefore the changing from digital to
analog and vise versa is modulation and demodulation.
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Mike Walsh
Guest
Posted: Sun Oct 30, 2005 8:44 pm    Post subject: Re: Modem name and function? Reply with quote
Because it modulates / demodulates a carrier signal.

species8350 wrote:
Quote:

A modem takes an analog signal and converts it to a digital signal, and
vice versa. So a modem is an analog to digital converter. So why is it
called a modem (modulator/demodulator)?

Thanks

--
Mike Walsh
West Palm Beach, Florida, U.S.A.
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Gerard Bok
Guest
Posted: Mon Oct 31, 2005 1:11 am    Post subject: Re: Modem name and function? Reply with quote
On 30 Oct 2005 03:41:39 -0800, "species8350"
<not_here.5.species8350@xoxy.net> wrote:

Quote:
A modem takes an analog signal and converts it to a digital signal, and
vice versa.

No, not exactly.

Quote:
So a modem is an analog to digital converter. So why is it
called a modem (modulator/demodulator)?

A modem is a device that takes a digital signal and converts it
into something that can be transferred over an incompatible
medium.
Mostly: transmit digital data over voice grade telephone lines.

A true analog to digital converter can convert any analog signal
into its digital representation.
A true digital to analog converter can convert any digital value
or stream into an analog signal.

A modem can only convert a digital datastream into some type of
'sound' that is compatible with the telephone system.
And a modem can retreive the same datastream from the received
'sound'.

The way a modem accomplishes this is by modulating sound (or
noise) in such a way that the receiving modem can reconstruct the
digital datastream.
And this can be done from very basic (one note for digital high
and another note for digital zero, as in 300 Baud systems) to
extremely complex systems, like V90 or V92.

--
Kind regards,
Gerard Bok
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species8350
Guest
Posted: Mon Oct 31, 2005 4:48 pm    Post subject: Re: Modem name and function? Reply with quote
Thank you

Good clear explanation

Best wishes

Sp.
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