Using a facsimile machine is as easy as using a copy machine. But you can also use your personal computer as a fax machine.

IBM PC and Macintosh users have several options. A fax modem allows you to send and receive. A regular data modem, along with a subscription to an electronic mail service, allows you to send text-only faxes.

The fax modem, also known as a fax board, allows your PC to send and receive fax messages. Prices range from less than $200 to more than $1,000. Some fax modems are external and plug into your PC or Macintosh serial port. Others are on circuit boards that plug into an expansion slot on an IBM compatible PC. Some operate at full speed, 9,600 bits per second (bps), but others work at only 4,800 bps.

What are the advantages of using a fax modem to send computer-generated documents? To begin with, computer-generated outgoing faxes are a lot better looking than the ones sent via regular fax machines. That's because the image doesn't have to go through the degradation of the fax machine's scanner. Another advantage is that computer-generated faxes can be more easily automated. Most of the fax modems come with software that allows you to create directories of people you send faxes to. To send a fax, you just select the recipient(s) from a menu and press a key. What's more, you can schedule the faxes to go out at any time. You can also use your software to generate junk fax mail -- just what the world needs.

Fax modems also allow for some interesting and useful applications. Quarterdeck Office Systems, for example, uses its fax modem to automate the sending of technical support bulletins to its customers. If a customer calls with a question that can be answered in writing, the technician presses a few keys on his or her computer and the company's fax modem, which is connected to its local area network, dials the customer's fax machine and sends out the appropriate bulletin.

Confidentiality is another advantage. Incoming faxes wind up on the recipient's hard disk instead of the fax machine's tray. They also save paper and laser printer supplies by eliminating the need to print a copy.

But there are some disadvantages. First, it's more work than using a fax machine. You'll have to fool around with plug-in cards, cables, software and configuration files. Instead of walking up to the fax machine to insert a sheet of paper, you have to load in memory-resident software, configure special modem drivers and figure out how to get the fax software to work with all the other programs on your machine.

And when it's time to receive a fax, you have to make sure that your PC is on and be certain that the fax software is running either as your primary program or in the background.

If you receive an incoming fax, you have to read it on your screen or print it out -- yet another step. What's more, if you want to send a copy of a brochure, newspaper article or other document that's not in your computer, you'll have to scan it first. Add one more piece of equipment and one more step.

Nonetheless, if you decide to try a fax modem, you can choose from a wide range of systems. One of the best deals for users of IBM compatible systems is the Fax96 from Fremont Communications of Fremont, Calif. This product, which plugs into a PC, costs $195 and comes with software that allows you to send and receive faxes in the background, add an optional cover sheet, broadcast multiple faxes or send at a delayed time. It also logs incoming and outgoing faxes and allows you to print or view incoming faxes on screen. Fremont Communications can be reached at (415) 438-5000. Fax: (415) 490-2315.

For portability, consider Touchbase Systems's $699 WorldPort. This pocket-sized fax and data modem runs on batteries and plugs into the serial port of a laptop or desktop PC. The company, located in Northport, N.Y., can be reached at (516) 261-0423.

Macintosh users should consider Abaton Technology's $599 InterFax, which serves as a 2,400 bps data modem and a 9,600 bps fax modem. It sends and receives in the background and lets you use the regular print commands to "print" your document to a fax machine, anywhere in the world. Abaton can be reached at (800) 444-5321.

But you don't even need a special fax modem to send text messages from your PC. If you have a regular data modem, you can connect to MCI Mail, CompuServe or AT&T Mail and use those services to send out faxes. It's relatively inexpensive.

Readers' comments are welcomed, but the author cannot respond individually to letters. Write to Lawrence J. Magid, P.O. Box 620477, Woodside, Calif. 94062, or contact the L. Magid account on the MCI electronic mail system.