starting out
COMMUNICATING COMPUTERS
Getting online with your Atari
by MICHAEL CIRAOLO, Antic Associate editor
For many computer hobbyist as well as businessmen and professionals, the greatest value of a computer is its ability to connect with other computers – mainframes or microcomputers – around the country.
This connection is called telecommunications, or sometimes telecomputing. It lets you meet other people with similar interests, bank and shop electronically, obtain programs and information over the phone, and much more.
The heart of comunications between computers is a modem (shortened from MOdulator/DEmodulator). A modern converts (modulates) data from your Atari into a signal suitable for transmitting over a phone line. It also converts back (demodulates) the transmitted signal into data understandable by anothcr computer.
To link up, each computer needs a modem. You also need to connect your modem and computer, and establish a connection (usually via telephone) between the two computers (see Figure 1).
RS-232 HOOKUP
The data communicated is nothing more than a series of electrical impulses sent between two computers, and a standard has been created to insure the compatibilty of these signals.
That standard is called RS-232C, established by the Electrical Industry Association. It defines voltage and resistance for signals between computers.
From the standard, we get the design specifications for the RS-232 port, an outlet found on many computers, and for the RS-232 cable, used to connect modem and computer.
Some computers, such as the new Atari ST series, have an RS-232 port built in. Other personal computers – including all other Ataris – do not include an RS-232 port.
There are two ways around this. You can buy one of the few modems that plug directly into your Atari, or use the Atari 850 interface which provides an RS-232 port. (Both of these alternatives are covered more fully in an adjoining story.)
MODEM MAPPING
There are a number of widely used terms that describe the different ways that modems do their jobs:
Direct-connect or acoustic: Early modems, and even some that are still being made, were primary acoustic modems. These have large rubber cups into which the phone handset is fitted. Unusual shapes such as Mickey Mouse phones won't work here. New phones and the latest modems can be connected directly to one another. These direct-connect modems plug into the phone line's modular plug.
Baud: How fast information is transferred, in bits per second, also abbreviated as bps. The modems at each end must operate at the same rate in order to communicate. Today's commonly used rates are 300 bps and 1200 bps. Just starting to appear on the consumer market are 2400 bps modems.
Duplex: Can information be sent and received from both computers simultaneously? If so, it is full duplex, like a telephone conversation. If both computers can send and receive, but not simultaneously – like CB radio – the connection is half duplex.
Auto-answer: An auto-answer modem can automatically answer the telephone, when properly connected to the computer.
Auto-originate or auto-dial: This means a modem is capable of dialing another computer, from keyboard commands.
Smart modems: Modems that are capable of autodial, autoanswer, automatically disconnecting if there is no carrier tone, and so on, are said to be "smart."
The capability of a modem is described by a set of standards separate from the RS-232C standard, which were pionered by Bell Systems. The Bell 103 standard means the modem works at 300 baud with full duplex. Bell 202 represents 0 to 1200 baud with half duplex. Bell 212 is full duplex, 0-1200 baud.
After a modem is connected to your computer, you need the proper software to operate the entire system.
TERMINAL SOFTWARE
Telecommunications software, also called terminal software lets you send and receive files and programs over the phone, store these files to disk or cassette, print out files and so on.
Just as there is a convention regulating the nature of the electrical impulses sent between computers, there are standards, called protocols, governing the format of information exchange
The Christensen (XMODEM) protocol, for example, is a common protocol used to transfer files from one computer to another. The receiving computer sends a certain signal every few seconds until the sending computer responds with an acknowledgement. This synchronizes the two computers, and is immediately followed by the file.
Terminal software also checks transmitted files for accuracy, because interference on telephone lines can destroy data in transit. This is called corruption.
To guard against data corruption, modems and modem software use several forms of error detection, called parity checking, checksum, and redundancy checking. These compute values for each batch of data sent, and send that value back to the transmitting computer. If the values don't match, the data is sent again.
CABLING COMPUTERS
You can use telecommmunication techniques without a telephone to transfer text files between different makes of computers. For instance, you can upload text files from a portable computer like the Radio Shack M-100 to your Atari. Or you can transfer a simple Logo program from your older Atari to the new Atari ST.
In general, transferring files requires an RS-232 cable to connect the two computers in lieu of a telephone connection, an Atari 850 interface, and a null modem cable or adaptor.
A null modem cable simulates the connection between computers created by modems. It lets you connect RS-232 ports directly (Figure 2).
The null modem cable takes the send signal from one computer and routes it to the receive channel of another and vice versa. These adaptors are available from Radio Shack for $29.95.
The cheapest and most instructive way of obtaining a null modem cable, however, is to make your own. You'll find a more detailed instructions in the July, 1984 issue of Antic, page 45.
GOING ONLINE
Once you've dressed up your Atari for telecommunications, you need numbers to phone. Elsewhere in this issue you'll find a story describing some of the best places to begin calling.
Also, listed below are some good reference books to get you started. Now, with your Atari and a modem, the world is yours. Just be carefull not to run up humongous phone bills!
SUGGESTED READING
For the hook-up
DATA COMMUNICATIONS FOR MICROCOMPUTERS
by Elizabeth Nichols, Joseph Nicols and Keith Musson
204 pages, softbound
McGraw Hill, 1982, $16.95
TECHNICAL ASPECTS OF DATA COMMUNICATIONS
by John McNamara
330 pages, hardcover
Digital Press, 1982 (second edition)
For going online
HOW TO GET FREE SOFTWARE
by Alfred Glossbrenner
436 pages, softbound
St Martin's Press, 1984, $14.95
GET CONNECTED, A guide to telecommunications
by Tom Kieffer and Terry Hansen
424 pages, softbound
Ashton-Tate, 1984, $24.95
STALKING THE ELUSIVE 850
The Atari 850 Interface Module is a small but versatile box sold separately from your computer. It connects to Atari computers with a standard serial I/O cable.
The 850 interface converts data from the computer into formats compatible with the RS-232 serial standard which is used by most modems, and also for the Centronics parallel standard which is used by most printers.
If you do not have an 850 you are restricted to using those few modems that plug directly into a port on the Atari computer – the Atari 1030 ($79.95 from Antic Arcade catalog) or the MMP-1000C ($149.95, Microbits Peripheral Products).
For printer compatibility, without an 850 you must use either an Atari-made printer or purchase a parallel printer interface such as the MicroPrint ($69.95, Microbits). For a full list of printer interface cables available, see page 33 of the March, 1985 Antic.
It usually is not easy to find an 850 at your local computer store, even though Atari has told Antic that it still has plenty of units available in their warehouses. According to one of our Atari sources, many nonspecialized computer outlets do not really understand the many uses of the 850 interface as a tool for advanced computing and so they do not keep it in stock.
In order to help readers get around this unavailability, Antic is printing here a list of dealers offering the interface module by mail. Prices vary widely, but all of the firms listed below offer a 90-day service warranty. We checked with each company, and were assured that they have a continual supply of 850s available.
DEALERS
AMERICAN TV
15338 Inverness Street
San Leandro, CA 94579
(415) 352-3787
$135
B&C COMPUTERVISIONS
3400 El Camino Real
Santa Clara, CA 95051
(408) 554-0666
$160
COMPUCAT
24500 Glenwood Highway
Los Gatos, CA 95030
(408) 353-1836
$117.31
COMPUCLUB
P.O. Box 652
Natick, MA 01760
(800) 631-3111
$112
COMPUTER CREATIONS
P.O. Box 292467
Dayton, OH 45429
(800) 824-7506
$109
COMPUTER PALACE
2160 W. 11th
Eugene, OR 97402
(800) 459-8013
$139.50
ELECTRONIC ONE
P.O. Box 13428
Columbus, OH 43213
(614) 864-9994
$87
SAN JOSE COMPUTER
1844 Almaden Road
Unit E
San Jose, CA 95125
(408) 723-2025
$149
GIZZMOZ
P.O. Box 1402
Concord, MA 01742
(800) 225-5800
$109.95
GETTING CONNECTED
DOW JONES SERVICE
P.O. Box 300
Princeton, NJ 08540
(609) 452-1511
(800) 257-5114
The grandaddy of all online services strarted as a stock quotation wire during trading hours. Your need for such information cannot be better satisfied, even though a number of other services now include stock quotes.
Dow Jones (DJ) owns the "Wall Street Journal" and "Barrons", offering them electronically, along with up-to-the minute financial news. Profiles of 10,000 companies are also on file. Dow Jones rates are $72 per hour during the day and $12 per hour at night.
PLATO
Control Data Publishing Co.
P.O. Box 261127
San Diego, CA 92126
(800) 233-3784
(800 233-3785 (in California)
Years ago, CDC and the University of Illinois collaborated to develop a computerized system for presenting and managing educational material. The result is PLATO, containing over 200,000 hours of structured "lessons" on most topics imaginable. Until recently, PLATO was restricted for technical reasons to expensive terminals, but the long-promised $50 cartridge from Atari now promises to make PLATO available to you for only $5 per evening hour.
THE SOURCE
1616 Anderson Road
McLean, VA 22102
(703) 734-7540
(800) 336-3330
The Source attempts to provide a more refined general information service than those offered by other non-specialized databases, but it doesn't quite achieve the quality of specialist like Dow Jones and Dialog. The service's $100 registration charge is stiff (but it is often discounted). Access rates are generally high – $7.75 per hour for evenings and weekends – and there's also a $10 minimum charge per month. Its services and information are similiar to CompuServe's, but you should compare the two before signing up with either system.
BRS AFTER DARK
3 Blackstone Street
Cambridge, MA 02139
(617) 491-3393
(800) 833-4707
Powerful professional databases such as BRS After Dark are available at a fraction of their normal cost when accessed after business hours. BRS, for Bibliographic Retrieval Services, is a medical, technical and scientific service during the day. It also offers data on a number of scientific and technical fields. You pay $50 up front, plus fees from $6 to $15 per hour, depending on which of the service's 25 databases you use. The minimum charge is $12 a month.
COMPUSERVE
5000 Arlington Center
Box 20212
Columbus, OH 43220
(614) 457-8600
(800) 848-8199
First home of the ANTIC ONLINE electronic edition and SIG*Atari, CompuServe dominates the home market for online services. Comparitively inexpensive to join and use, CompuServe offers a wide varity of services including programming, storage, bulletin boards, shopping, electronic mail, airline reservations, and real-time communications as well as raw information. Its main news source is the Associated Press.
Sign-up details are available at most computer stores. Night rates are $6 per hour for 300 baud and $7.75 for 1200 baud. There are surcharges for some premium services. The $40 entry fee is often reduced or waived as the result of various promotions.
DIALOG
3460 Hillview Avenue
Palo Alto, CA 94304
(415) 858-3785
(800) 227-1927
Space research gave rise to the Lockhead subsidiary Dialog. During working hours, its 200-plus databases serve more than half a million users at prices we needn't describe. At night, the service's most popular databases are available through a service called Knowledge Index, which specializes in medicine, psychology and business. This service costs $24/hour. There is no minimum charge, but you must buy a $35 instruction manual (consider it a fee for the two free hours you're given to learn the system). Hardcopy printouts of desired material are reasonably priced.
DELPHI
3 Blackstone Street
Cambridge, MA 02139
(617) 491-3393
(800) 544-4005
Delphi is undergoing great changes. Not only is SIG*ATARI going to be duplicating its files on Delphi, but so is ANTIC ONLINE. Delphi offers news, electronic mail and searchable databases, but specializes in user-created files, which may be either public or private.
You can write, edit and store files while connected to the system, or upload material created offline. You can keep your calendar up to data, contribute to collaborative novels, publish a newsletter, register your opinions, seek expert advice, or confer in real time with other users. Life-time registration is regularly $50, which includes two free evening hours. Rates are $16 during the day, and $6 in the evenings for either 300 or 1200 baud. There is no monthly minimum.
BOISE USERS GROUP (BUG)
1030 El Pelar Drive
Boise, ID 83702
(208) 383-9547
One of the most useful bulletin board services for Atarians, BUG offers a downloadable list of over 400 other Atari bulletin board numbers. These numbers are listed by state. And they are verified biweekly to ensure accuracy. This is probably the best source of information on Atari bulletin boards for your area.
ATARI USERS GROUP BBS
1196 Borregas Ave.
Sunnydale, CA 94086
(408) 745-5308
Operated by Atari Corp., this BBS is just getting started. It will provide some general information and a national listing of users groups. We are told that more is planned for the future.