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A modem is electronic device or computer program that establish the transition of the data over the telephone line
A modem is electronic device or computer program
that establish the transition of the data over the telephone line. The term
“modem” originated from
“modulator-demodulator”. Modem converts the data from
digital format to analog waves and back. The analog waves can be transmitted
over the copper telephone line. There are two types of computer modems external
and internal. External modems can be attached to mostly any personal computer
with RS-232 port. The internal (onboard) modems come as an expansion board that
has to be inserted into a vacant expansion slot.
There are number of different protocols for formatting
data to be transmitted over telephone lines. Official standard protocol is CCITT
V.34 and a lot of others have been developed by independent companies. Most of
slow speed data transmission modems support common transfer protocols. High
transmission speeds, however, based on less standardized protocols.
In addition to transmission protocols modem can be
distinguished by the following characteristics:
bps : (bits per second) It tells the wow
fast the modem can transmit and receive data. The fastest modems run at 57,600
bps, although they can achieve even higher data transfer rates by compressing
the data. Obviously, the faster the transmission rate, the faster you can send
and receive data, but you cannot receive data faster than it is being sent.
voice/data: Many modems support two modes: voice
and data. In data mode, the modem acts as a regular modem. In voice mode, the
modem operates as a regular telephone. Modems that support voice/data modes have
a built-in loudspeaker and microphone for voice communication.
auto-answer : An auto-answer modem enables
your computer to receive calls in your absence. This is useful if you are
offering some kind of computer service that people can call in to
use.
data compression : Some modems perform
data compression, that improves the data transfer rates. However, the modem at
the other end has to be able to decompress the data using the same compression
technique.
Fax capability: Most modern modems are fax
modems, which means that they can send and receive faxes over the telephone
line.
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