Classic Computer Magazine Archive COMPUTE! ISSUE 54 / NOVEMBER 1984 / PAGE 32

Understanding Modems

Sharon Darling, Research Assistant

While your computer is capable of doing thousands of jobs, from functional to recreational, there is one peripheral you can buy that will open up a whole new world of computer—a modem. With a modem, you can communicate over ordinary telephone lines with other computers also equipped with modems.

Basically, a modem performs two jobs. At one end, the modem transforms the digital information from the computer into analog sounds that can be transmitted over the phone line. This is called modulation. The tones sound like high-pitched whistles, each blip and beep representing an individual bit of data. At the receiving end, the second modem translates the analog tones back into the original digital information (demodulation). Hence the term modem (modulator-demodulator). Coupled with terminal software that tells your computer how to communicate with another computer, a modem puts you in business to tele-communicate. (For a few more fundamentals, see "Bulletin Board Basics" elsewhere in this issue.)

While the basic job of modems is to serve as signal converters and translators, they are becoming more and more sophisticated. The new breed of modems can automatically dial phone numbers, answer phone calls, sign on to commercial information services, retrieve data, and perform other tasks under program control with no human intervention.

That's not to say that people aren't buying less expensive modems—they are, and in great numbers, says Jerry Hussong, director of consumer sales for Anchor Automation, Inc., a modem manufacturer. "People are buying [inexpensive modems] and they're having a great time with them. Then they come back a couple of months later and say, ‘Hey, this is nice, but I'm lazy—I want something that will automatically answer the phone.’"

Besides making modems more sophisticated, modem designers and programmers are also trying to make the devices easier to use. They're trying to overcome the intimidation some people feel when they sit down to a desk filled with new technology—especially computers and modems. But that fear should fade as more people become involved with personal computers, manufacturers feel.

"People are not so much intimidated by telecomputing as they are by the whole idea of computing itself," says Nick Wreden of Hayes Microcomputer Products, Inc., a pioneer in sophisticated modems for personal computers. They're not just scared of a modem, they're scared of everything connected with a computer."

Modems, computers—no matter how sophisticated we all claim to be—are scary," adds A.W. Johnson, a vice president at Code-A-Phone Corporation. "They take us out and test our ability to learn, our ability to understand new things, and to remember and use the new tools. Risky business, because we might expose our ignorance."

Code-A-Phone makes a new telephone with a built-in modem. It's designed for business use and should help people get used to new technology, says Johnson, because "it's a nice, plain-looking, ordinary telephone that everybody feels comfortable with."

Sounds Or Silence

There are several things to consider before buying a modem. First you'll have to decide which type to get. Modems can be either acoustic-coupled or direct-connect. Acoustic modems were developed first and used to be cheaper and more popular, but lately direct-connect models have drastically dropped in price and are pushing many acoustic modems off the market.

Acoustic modems have a pair of soft rubber cups into which the telephone handset fits snugly. One cup contains a speaker, which generates the tones to be transmitted over the phone line, and the other cup contains a microphone, which in turn receives the tones sent by the other modem. If you listen closely to an acoustic modem, you can hear the high-pitched whistling of the tones being transmitted.

Acoustic modems have two main drawbacks: Many newer phones have nonstandard handsets which won't fit into the rubber cups; and since acoustic modems depend on a tight seal between the handset and the cups, a poor fit means the telecommunications link can be garbled by outside room noises.

Acoustic-coupled modems like this Atari model grip the telephone handset with tightly fitting rubber cups to keep outside noises from interfering with communications.

Direct-connect modems bypass the handset and the cups. They connect directly into any modular phone jack and work in total silence. Some direct-connect modems look like cartridges and plug into an expansion port on the computer, while others are stand-alone units that hook up between the computer and your phone. There are also interal modems which fit into the expansion slots inside some computers, and modems built into telephones, such as Code-A-Phone's Tel-A-Modem 212A.

Fast Talking

Another factor to consider when buying a modem is the speed at which it communicates. Naturally, faster modems are more desirable, but they also cost more. Modem speeds are expressed in bits per second (bps) or baud rates (the latter term is technically incorrect but commonly used). Modems for personal computers generally work at either 300 bps (roughly 30 characters per second) or 1200 bps (120 characters per second). Although some very expensive modems can transmit up to 9600 bps, ordinary phone lines have trouble with anything coming over the wires faster than 2400 bps.

Faster modems save money as well as time, because they cut long-distance phone bills and reduce the access time on commercial information services, which charge by the hour. At 1200 bps, words stream by faster than most people can read, so the better terminal programs let you capture everything and save it on your disk drive or printer for later perusal.

High-speed telecommunications in the future will depend on what phone companies can do to fix their lines, some of which have been in use since the 1920s, says Wreden. "As soon as they're upgraded to fiber optics or whatever, then you can speed up your transmission because you cut down line noise and that sort of thing."

Direct-connect modems, such as this Volksmodem, plug right into the modular phone jack ad are generally more reliable than acoustic modems

For today, 1200 bps seems to be the new standard in offices. When large files are being uploaded (sent) or downloaded (received), the extra cost of a faster modem can be recovered after just a few long-distance phone calls. But there's still a large market for the slower modems, explains Hussong, especially among home users. "There are too many local bulletin boards, and far too much out there available at 300…. If you're only getting on there to talk to some friends, or to read a bulletin board, there's no need to spend the money for a 1200—it's actually more intelligent and economical to be at 300 baud."

Other features that add to the versatility—and price—of a modem are auto-answering (the modem can taw phone calls from other computers by itself); auto-dialing (the modem can place calls by itself); auto-redialing (the modem automatically redials a call if the line is busy); and self-testing (the modem makes sure everything is hooked up and working properly).

Another consideration is the type of phone system you have. While some modems work with either Touch-Tone or rotary (pulse) phones, others work only with one or the other. Adapters are available to let certain modems work with certain types of systems.

like other computer peripherals, modems are not generic items. Some modems plug into RS-232 serial interfaces and will work with a number of different systems, while others are designed only for specific computers. Check advertisements and brochures carefully for this information.

Terminal software usually must be purchased separately, acquired through a user group, or typed in from a book or magazine.

Lower Prices Coming

Modem prices currently range from about $49 to $1000 or more. Last year the least expensive models cost about $80. A few years earlier they were hardly available for less than $200. Competition will continue to drive prices down, Hussong says, and by the end of this year 1200 bps modems should cost around $300–$500. In 1985, he estimates, 1200 bps modems will cost $250–$400 and 2400 bps modems should cost under $1000. A major force behind the lower prices is a new modem-on-a-chip designed by Texas Instruments. More computers are starting to come with built-in modems as a standard feature, too.

Code-A-Phone's Tel-A-Modem 212A is a telephone with a built-in modem and two phone lines for simultaneous voice and data transmissions.