The piece of equipment that allows a computer to communicate with other computers over telephone lines is called a modem. The modem allows the individual to access information from all overthe world and use that information in everyday life. Connecting with banks, Automatic Teller Machines, cash registers to read credit cards, access travel agents, buy products, e-mail,access databases, and teleconferencing, the modems provides easy access to many services. Files can be transferred easily, by uploading to another machine, or downloading to your own machine within a matter of minutes. The computer modem can be used as a telephone answering system, and documents can be faxed from one computer to another assuring fast and easy access to important documents.
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Does a modem really talk? Some people seem to think so. Modems really squawk at each other. A computer is a digital device, and communicates with other computers in a language made up of digits or numbers. That is why you hear a high pitched squawking or squealing sound when a modem is in use. The modem converts data into sound so that it can be sent through the phone system. The modem sends large amounts of data by sending combinations of tones at different frequencies.
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A modem takes computer information and changes it into a signal that can be sent over telephone lines. The modem is a bridge between digital and analog signals. The computer being of the digital type, and the telephone using analog technology. The modem converts the "0"s and "1"s ofthe computer (off-on switches)into an analog signal by modulating the frequency of the electronicwave or signal. The modem does just the opposite and demodulate the signal back into digitalcode. The modem gets its name from the MOdulate and the DEModulate.
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Most people believe that you need a separate phone line for a modem, but that is not true.Your modem and telephone can share one line, the problem arises when someone else needs to use the telephone while the modem is in use. Also disable call waiting, it could disrupt your modem connection while the modem is in use. In order for the modem to work you need some kind of communications software. This software manages the communication with other modems. When exchanging information, modems use the same speed. If the modem is communicating with a slower modem, both modems will communicate at the slower speed.This is determined by the "handshake" which is how modems establish the way they will communicate with each other.
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When one modem has successfully made connection with another modem, it is said
to be "Online".The speed of the connection is of course determined by the connection
with the other computer.The speed of the modem is measured in bits per second (bps).
Most modern modems currently run at 28,800 bps or 33,600 bps. The newest modems being
developed for the general public are 56K modemsbut have limitations, because most of the
hardware and software solutions have not upgraded to accomodate them. Another measurement
for modem speeds is in kilobits per second (Kbps). A 33,600bps modem would also be referred
to as a 33.6Kbps modem.
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There are three kinds of modems internal,external, and fax. All modems do the same thing, they
allow computers to communicate through telephone lines. This lets computers exchange
information everywhere.
- Internal Modem: This device is a circuit
board that plugs into one of the expansion slotsof the computer. Internal modems usually
are cheaper than external modems, but when problems occur, fixing and troubleshooting the modem
can sometimes prove to be quite difficult. The telephone line plugs into the modem port
in the back of the computer.
- External Modem: This device attaches
to the back of the computer by way of a cable that plugs into the modem port.
It is usually less expensive and very portable. It can be used with other computers
very easily by unplugging it and plugging it into another computer. (Remember that you need
the right modem software on all the computers you wish to use the modem with.)
- Fax Modem: This device can be hooked up to your telephone and used
to send information to your computer. Your computer can also send information to a fax
machine. Most computer modems are modems with faxing capabilities.
- ISDN Modem: The ISDN modem requires a special phone line called an ISDN line.
This modem sends data at a very fast rate. (56K). The advantage of this modem is that it is very fast and is able to transfer data and graphics at an amazing speed with very little interference. These modems and lines tend to be quite expensive.
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