Modems: your gateway to the Internet - ADSL 2+, ADSL broadband, 56K dial-up

The little boxes that sit beside (and provide Internet access to) most computers in the world today are often taken for granted. But it was not really so long ago that a “modem”, otherwise known as a modulator-demodulator, first became a household item. It is important to have a modem that can fully handle your chosen connection speed; after all, it's hardly reasonable to expect a modem intended for dial-up to cope with the blazing pace of ADSL 2+.

How do modems work?

The main use of a modem is to send digital information over a phone line. It acts a type of signal box between a computer and the telephone network. Typically, there will be two modems in operation to make a connection complete: one between a PC and the phone line, and then another between the phone line and the server.

Here is where the expression ‘modulator-demodulator’ becomes important. The modem connected to the computer that is sending information "modulates" (or "adjusts") the digital data so that it is compatible with the analogue phone line. Then, the receiving modem demodulates that information back into digital data, ready for the computer to receive. Wireless modems work on the same principles, but instead convert digital data into radio signals and back again.

History of modems

The first modems to be introduced in the 1960s had a speed of 300 bits per second. Things remained this way until the late 1980s, and it wasn’t until 1998 that 56 kilobit per second (kbps) modems became the norm.

The introduction of asymmetric digital subscriber line (ADSL) revolutionised modems. Copper used in phone lines has a bandwidth much larger than the 3000 hertz that telephones are limited to. ADSL seized the opportunity to use all of the under-utilized copper wire between households and businesses and their telephone exchanges, resulting in a dedicated, digital superhighway.

With the popularity of ADSL 2+, and its connection speed of up to 24 megabits per second (mbit/s), 56kbps modems will soon be relegated to the shelf.

Types of Internet modems

There are four major types of modem available today: standard dial-up modems, standard ADSL modems, ADSL 2+ and wireless. The service you sign up for with your Internet Service Provider (ISP) will determine which modem is right for your needs.

Most electronic retailers will stock a selection of modems, as will most Internet providers. In fact, it’s worth checking your ISP’s contract first before going out to buy one, as they may insist on supplying you with one.

However, if you already have a modem, there’s no reason why you should have to foot the bill for a new one, even if you are upgrading from standard ADSL to ADSL 2+, unless you’re moving over to wireless.  Most ADSL modems on the market today are ADSL2+ configured as well. Some of these include:

• Netcomm NB5
• D-Link DSL502T
• Netcomm NB9W
• D-Link DSL504T
• D-Link DSLG604T
• ZyXel P2602H
• ZyXel P2602HWL
• Netgear DM111P

If you are looking for a suitable modem for your Internet connection, consider what your needs may be in the future; it's best to have a modem that can handle more than you need, rather than less. Given that the maximum connection speed of ADSL 2+ is 24 mbit/s, a modem equipped to handle that connection should see you through for a while yet.

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