FAX: A New Hobby (May, 1987) ---------------------------- By Bernie S. Occasionally when scanning phone numbers you'll come across what sounds like a computer modem carrier but isn't. What it often turns out to be is a facsimile (FAX) machine. For those unaware of it, a FAX machine lets you send printed info (text, diagrams, or photos) over a phone line or radio link. Like computer modems, they use a carrier tone, but it is a different frequency and unlike "normal" data communications. A FAX machine scans a printed document using an optical sensor that sweeps over the print detecting light and dark sections of the paper. There are presently three common FAX standards in use: Group I, II, and III. Until fairly recently, most FAX transmissions were of the Group I variety. Group I machines (many of which are still in use) use a rotating drum that the document is clamped to while the sensor traverses the length of the drum slowly. The light and dark sections modulate the carrier tone frequency which is transmitted over the phone line to another FAX machine. At the other end, it works in reverse - the modulated tone is translated back into an image by a hi-voltage stylus, which scans over a blank sheet of electrostaticly-sensitive paper, "burning" the image onto the sheet. (This makes a rank smell; real old machines would fill a room with smoke!) Group I transmissions typically take 6 minutes for an 81/2 by 11 inch sheet. With the advent of cheap digital IC's, Group II and III standards emerged which transmit signals digitally (not unlike computer modems). The fastest group III machines can send a document in less than a minute at 9600 baud, the limit for unconditioned dialup phone lines. A Group IV standard now exists which is much faster but requires Bell DDS or similar dedicated digital lines. The mechanical drum is now obsolete - a sheet is simply "dropped in" a newer FAX machine in which a tight row of phototransistors scans the whole document as it s pulled in between small motor-driven rollers. For output, ink-jet or similar printing technology prints out the received document. For experimenters with little (or no) money, a lot of companies are getting rid of their older Group I and II machines for cheap I got an Exxon Quip 1200 Group I FAX from a local newspaper for $50, and they threw in about ten reams of the special paper. This model was very popular about six years ago, and sold for about $1000. Look around! Most Group II and III machines can be switched into Group I mode for compatibility. Some newer machines double as copiers, though you can cheat and use a tape recorder to "play" a document back into a machine to get a copy in a pinch. Eventually, a FAX machine/laser printer/copier will be invented and will be a standard office machine everywhere. Expensive PC add-on cards exist that convert a PC and printer into a fax that ll store images on disk, but they're almost as expensive as a new FAX machine! Now we can all send schematics, drawings, and photos over the phone for cheap - just like the big boys do. I may be the first to coin a new term: PHAXing! As an added bonus, if you have a shortwave receiver with a BFO, you can pick up FAX images relayed from weather satellites, wire and press service photos, etc. before everybody else sees them. Some minor modifications are needed to convert the speed since they use nonstandard scan rates, but it's worth the effort. I hope you're all tuned on to this "new" hobby. Let's see some enthusiasm and support for FAX!