A modem is a device that allows two computers to communicate over a standard phone line. This is accomplished by changing the digital information of a computer (which is stored as a series of 0's and 1's known as the binary code) into a tone, or frequency, that can be sent over the phone to another modem. The receiving modem will then change the sent tones back to digital information, which can be understood by the receiving computer. This process gives the modem its name, derived from the two words modulate and demodulate, which accurately describe the two primary functions of a modem.
There are two types of modems -- internal and external. An internal modem is placed directly into a computer's communications (COM) port, which is located inside the computer. The other type of modem, an external modem, is kept outside the computer. Internal modems are usually less expensive than their external counterparts. This is because external modems are both easier to install and more mobile.
Modem Speed (Baud Rate)
Modems transfer data in the form of bits (8 bits = 1 byte). Obviously, the more bits that can be transfered over a given amount of time, the faster the transfer of information will be. Well, the speed of a modem is usually derived from the number of bits it can transfer in one second, called bits per second (BPS). Another term which is used to describe the speed of a modem is baud rate, which doesn't technically mean the same thing as bits per second. A modem's baud rate is actually a measure of how many changes in tone (or frequency) can occur in one second. Since the average computer user is not concerned with the subtle differences in these definitions, the two words are often used interchangeably.
Some common modem speed increments (BPS) include:
Obviously, the faster the modem, the more expensive it will be. Although you can use a modem of any speed to access the Internet, there are definite advantages to having a faster modem (14.4 or 28.8). Everything will download faster, including E-Mail, Web pages, and files. This means you will spend less time on-line, and that could save you money if you pay an hourly connection rate. If a 28.8 or 36.6 modem isn't fast enough for you, there's always ISDN.
What is ISDN?
ISDN stands for Integrated Services Digital Network. As the name suggests, an ISDN phone line transfers pure digital information, unlike a standard phone line that was designed solely for voice (analog) communications. ISDN lines can transfer data at an amazing 128 kilobits per second, almost five times faster than a 28.8 baud modem. Although ISDN lines are not new (in fact, they've been around for nearly a decade), only recently have they been available to the public for a reasonable price.
Many Internet Service Providers and Online Services are now offering customers Internet access through ISDN lines. In most cases, the actual lines have to be purchased through your local phone company. Monthly fees for use of an ISDN line are usually around $25 to $75, depending on your local phone company. There is also usually a setup fee which can be anywhere from $125 to $225, also depending on your local phone comapny. In recent months, many phone companies have been waiving the ISDN setup fee, however, in an attempt to get ISDN lines installed into more homes, which would ease the transition period to digital lines which will occur some time in the near future.
Your local Internet provider will also probably charge you a little more for an ISDN account than a standard Internet account. In addition, you will need to purchase an ISDN adapter, which will run you anywhere from $200 to $700. Despite the apparent costs of an ISDN line, many Internet users feel it is worth it. Depending on your financial status, it might be. For a comparison, a file that takes 20 minutes to download on a 28.8 modem will take only about 58 seconds using ISDN technology. Another example: a web page that takes about 20 seconds to download on a 28.8 modem takes about 2 to 3 seconds on an ISDN line. The dramatically increased performance of ISDN lines on the Web is due to faster initialization communications with remote Internet sites.
Communications Software
With a SLIP or PPP Account, your computer is directly connected to the Internet. Because of this direct connection, your computer must be able to communicate with the Internet. This can only be done by using software that "speaks" the language of the Internet. This language is called TCP/IP, which stands for Transmission Control Protocol/Internet Protocol.
TCP/IP is the standard language of the Internet and your computer, like every other computer connected to the Internet, must have some sort of TCP/IP "translator." This is where your TCP/IP software comes in. This software is necessary for any communications to be done over the Internet. In most cases, your TCP/IP software is also used to connect with your Internet provider (in other words, dial their modem) and establish a connection. It is because of this feature that TCP/IP software is often referred to as a TCP Dialer.
Check out NetGuy's Winsock Utilities list for links to some TCP Diallers available for download on-line.