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MODEM

Modem (mō´dem) (n.) Short for MOdulator-DEModulator. A modem is a device or program that enables a computer to transmit data over telephone or cable lines. Computer information is stored digitally, whereas information transmitted over telephone lines is transmitted in the form of analog waves. A modem converts between these two forms.

In order to send and receive data over the Internet , modems have to process outgoing and incoming data streams. Hardware-based modems have special hardware chips onboard that do most of this processing. Because of this, hardware-based modems do not have to rely on sending information to and from the computer’s central processor, which can slow down transmission speeds and place a heavy drain on the computer for performing other tasks.

Aside from the transmission protocols that they support, the following characteristics distinguish one modem from another:

  • BPS : How fast the modem can transmit and receive data. At slow rates, modems are measured in terms of baud rates. At higher speeds, modems are measured in terms of bits per second (bps). The fastest modems run at 56kbps, 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.
  • Voice/Data: Many modems support a switch to change between voice and data modes. In data mode, the modem acts like a regular modem. In voice mode, the modem acts like a regular telephone. Modems that support a voice/data switch 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 only necessary if you are offering some type of computer service that people can call in to use.
  • Data compression : Some modems perform data compression, which enables them to send data at faster rates. However, the modem at the receiving end must be able to decompress the data using the same compression technique.
  • Flash memory : Some modems come with flash memory rather than conventional ROM, which means that the communications protocols can be easily updated if necessary.
  • Fax capability: Most modern modems are fax modems, which means that they can send and receive faxes.

DSP modems have some of the processing capability of hardware modems, but not all. As a result, they are faster than softmodems but not as fast as hardware modems.

Softmodems must rely almost entirely on the computer’s CPU to process the data. As a result, they are the slowest modems and place the greatest burden on the CPU, which may slow down other applications running on your PC.

A modem determined by the best processor type for you:

  • Hardware Modem: If you will use your modem daily for several hours or more you should buy a hardware-based modem.
  • DSP Modem: If you plan to use your modem daily for an hour or more then a DSP modem would be the best choice.
  • Softmodem: If you plan to use your modem for simple Internet access a few times per week, a softmodem is probably the most suitable.
You should also consider your computer’s processor speed. In general, the slower your computer’s central processor is, the more powerful a modem you should purchase. This is because less powerful modems put more of a strain on the computer’s own processor. So you should only use a weaker modem (softmodem) if you have a fast central processor. You can check your processor’s speed by consulting the documentation for your PC. You can also check within Windows by selecting "Properties" on the "My Computer" icon.

A modem, also known as a dial-up modem or analog modem, can be confusing. There are several different form factors and processor options to choose from.

Modems come in 5 different form factors:

  1. USB Modem (external)
  2. External Serial Modem
  3. PCI Modem (internal)
  4. ISA Modem (internal)
  5. PCMCIA Modem or Laptop Modem (external)

To purchase the correct form factor, you should consider what options are available for your computer, the performance required, and the ease or difficulty of the installation.

  • USB Modem: If you have a USB port available (either USB 1.0, USB 1.1, or USB 2.0) you might consider a USB modem. They are the easiest modems to install, since they do not require you to open your computer case. USB modems can usually be found in DSP and hardware-controlled versions.
  • External Serial Modems: Like USB modems, serial modems are external and easy to install. They are usually hardware controlled and offer excellent performance.
  • PCI Modems: These are the best-selling modems, and are generally the kind of modem that comes installed a new machine. PCI modems come as either DSP modems or softmodems. You should only purchase a PCI modem if you are comfortable opening your PC case and installing a new PCI card.
  • ISA Modems: These are also internal modems. To use an ISA modem, your PC must have an available ISA slot. These slots or usually only found on older PCs. Consult your system documentation to verify your slot type. These are usually hardware controlled modems, sometimes DSP-based.
  • PCMCIA Modems or Laptop Modems: This is a "card"-type modem that can be used only with a laptop. If you have both a laptop and a desktop PC, you might want to purchase a USB modem instead, since it can be used with either type. For simplicity and ease in traveling, a PCMCIA modem is the best choice.

Modem Vendors:

  • Diamond Multimedia
  • Best Data Products
  • U.S. Robotics
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