The History of the Modem
Essay Preview: The History of the Modem
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The modem, which is an acronym for modulator/demodulator, was invented in the 1950s for military use. Manufactured by the now popular computer company, IBM, modems were used as part of an air-defense system; their purpose was to connect various airbases and control centers. Modems are devices that mix (modulate) and separate (demodulate) signals, allowing one computer to connect to another. They transfer the data over telephone lines by using analog waves and the modem then converts the waves back and forth. The first modems were designed to hold a telephones receiver in a cradle and had wire connections that went from the cradles to the computer. Today, most modems are either internal or external hardware devices.
Before the computer modem, there was the com-port. When an internal modem card is placed inside of a computer, it behaves as a COM2 or COM3 port. It is also possible connect serial mice into one of these ports (Gilbert, 1996). Asynchronous communication is used in the PC COM port. Each byte of data is a separate unit and the computer that is sending the data can pause between any two bytes of the message. However, the receiver of the message may have to catch the data as quickly as it arrives. This is done by the “a synch” data requiring one extra bit worth of time to announce the new bytes beginning and once extra bit worth of time at the end. This is what is known as the “start” and “stop” bits. This means that a 2400 baud modem could transfer only 240 bytes of data per second. Each byte would require a minimum of 10-bit times. This was once called “start-stop” communication, but asynchronous (a sync, for short) is the name (Gilbert, 1995).
The modem does not start and stop the bits. They are actually put out as part of the general data compression. The start and stop bits continue to be generated on the wire that connects a COM port to an external modem. The modem COM port is generally configured to use a higher speed between the modem and the COM port than what the actual transmission will support. A modem may operate at 14,400-kbps with the COM port configured for 38,400-kbps. This is an example of older technology being adapted to meet new requirements (Gilbert, 1995).
Currently, there are several different types of modems that are used in both everyday life and business. In 1994, the standard modem speed was set at 28.8 kbs; it was called the V.34. “At one time just the thought of standardizing a 9.6-kbps modem was amazing. People wondered what the possible applications could be.” (Mannes, 1995) Now, speeds are much faster and technology has grown by leaps and bounds.
Ray Wright, director of marketing for Motorolas modem products, says that a V.34 modem can “learn”, so to speak, which parts of the spectrum are clearest for the transmission of data. The V.34 standard uses data-compression technology to reach speeds of up to 115.2 kbps between two computers. This, however, may vary if the files being transferred are already zipped (Mannes, 1995).
The cable modem, unlike the original, does not connect through phone lines. Instead, they connect through the same coaxial cable that your television does. In order to connect to the internet using a cable modem, your computer must be equipped with a NIC (Network Interface Card) card, which attaches directly to the motherboard.
“There are only two drawbacks to cable. First, it is a shared connection, meaning you share the “pipeline” with your neighbors. That doesnt mean that your neighbors will know what you are doing on the internet. But it does mean that if all of your neighbors were on the internet downloading large files at the same time, your internet connection would not be as speed as usualThe second drawback to cable is also minor. Because cable modem connections are always, they, like DSL connections, make you more vulnerable to hacking and security breaches. For this reason, many cable companies are now providing their customers firewall software to help protect their security.” (Berger, 2005)
DSL which stands for digital subscriber line is another form of broadband connection. Unlike the cable modem, the DSL connection goes through the telephone line. Both of them, however, use an external modem to make the connection. Since DSL connects through the phone it is necessary to use what is called a “micro-filter”. This device is placed between your telephone line and the wall-jack and enables the external modem to operate on a different frequency than the telephone itself. That way its possible to talk on the phone while youre on the internet, making business much easier.
For computers to contact each other, the modems must have similar settings. Those settings include the rate at which the data is sent and received, the parity, and data bits. The rate at which the data is received is referred to as the baud rate. It generally ranges from 300 to 28,800