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e.rns: Hooking Your Co:mputer to t.he World

by Stan Miastkowski

Personal computers are ralemed and useful beasts. Whether playing games, balancing checkbooks, or sending our invo ices, rhey've begu n tO have '3 pro­fo und influence o n our Iives. Bue a computer sitcing by irself on top cf che desk is srill pretty limired, Thar's why relecomputing, linking yo ur computer to ocher computers using the telephone tines, is cne c f the fasresr-growing areas a f the volarile personal compUl"er ficld.

"lnformacion utilities" like Com­puserve, Do w Jo nes. and T11e Source are pro liferating, making your video screen cruly a "window on the warld." (See Popular Compucing's "T elecam­punng colurnn every momh for spccific app licario ns.)

Getting Slarled Okay, you've del.:ided to expand your

pcrsonal co mpuccr, subscribe to one af the :icrvict!s , swap informatian wirh a

18 ;":1J\'enl~r 19S2 Popuhu C .>mputing

friend's computer, a r maybe even set up your own computerized bulletin ·board sysrem (CBBS) , Ir won'r rake you long to fincl out that emering the te1ecom­munications arca, with its own "language" and a whole new set af ac­cessories and peripherals to consider, is rouch like entering a fareign country.

The Telephone Nelwork Righr off, rhere's a major problem,

Computers are digital devices: every­th ing they do is in b inary forro, a string of ls and Os, On rhe orher hand, rhe natio nwide telephone network main­rai ned by rhe BeI1 Sysrem is an analog system. Voices are trans­micted as conscanrly varying volrages ovcr a pair of wi res. Obviously , in order for two compucers to communi­cate over the tdcphone lines, there has tO be some way to turn rhe digital signals imo <lna lag :lIld the anaiag signals back to d igital ·ar thc o thcr end.

The device that performs this trans­latio n is a modem (short for modularor/ demodularor), When you're sending data, the modem rakes a srream of digital information from your computer's RS-232C interface, turns it inca tones (one tone fo r. 1, anm her for O), ancl sencls it o ut over çhe celephone lines. At rhe receiving end another modem does the exact opposite, trans­laring rhe tones back imo digiral dara,

Measuring Speed Alrhough a modem's job sounds

relatively simple, chere are quite a few complicating facrors. Befo rc we loo k at some of the prablems of sending dara Qvcr telepho nes lines, lec's look ac speed. Data communicacio ns speed is measured in bits per second (bps) , which is more ,:ommonly referred to a.s baud. Bccause data is sem ovcr telephone lines in serial fa.shion (one b it at time), baud is a. mensure af the number a f bits chat pass a given point

Hlustration by Aobert Tinney

in a second . The most common speed you'lI hear about is 300 baud. Although that sounds fast, remember that it takes as least 7 bits to represent a character using the standard ASClI (American Standard Code for Information Inter­ch ange) code. In a data communica~ tions setup, extra bits are added to this computer "word" to reli the computer on the orher end where a character starts and Stops. This ali \Vorks down to about 30 characters per second, a speed just fast enough to read comfortably but terribly slow if you're sending hun~ dreds of pages of data down a tele­phone line.

How Fast Can You Go? It would be great if vou could send

data across standard telephone !ines as (ast a~ Vou wamed . (It would save on those long-distance phone bills.) Unfor­tunately, limiting facrors existo Although the United States has by far the best and most reliable telephone system · in the warld, ir's subject to noise, c1icks, echo, and orher in~

ter(erence that can garble a signal. That's one reason why data must be sent comparatively slowly: each tone must be long cnough for the modem to recognize ir in case of interference.

The biggest limiting factor is a bit more technicaI. It's called band\Uidth. It's an immurable law of electronics

that the fasrer Vou send information, the more "room" ir takes up in the elec~

tTomagnetic spectrum. For comparison purposes, think of how we hear . Most human ears hear tones in the range of 20 to 20,000 hem (cyeles per second). But the nationwide telphone network is designed primarily for voice, a range of only 30 to 3000 cyeles per secando Ali the telephone lines Vou cannect to

when Vou pick up and dial your home or office telephone are designed to ·han~

dle tones only in that range. The telephone company calls them voice­grade lines. For various reasons, the fastest Vou can reliably send tones over voice~grade telephone !ines is at the 300 baud "standard" memioned above . (That's with both computers "talking" at once - like a normal two~way phone conversation.)

It's possible to exchange data faster, although it requires some fancy foot~

work. A standard telephone line can send data at 1200 baud (120 characters per second) in one direction at a time. Some 1200~baud systems manage two­way conversations by actually using two telephones at the same time. (For a discussion af what these "one-way"/ "two~way" conversations mean, see d uplex below.) Full two-way 12oo-baud communicarions can be done using special (and expensive) telephone lines. They're called conditioned !ines by the

telephone company and must be spe­cially ordered. (They also cast consider­ably more than a voice-grade line.) If you're using a personal computcr pri- . mari\y to access the information utilities, vou don't have to worr)' abo.ut conditioned !ines. They're mainl )' need­ed by rnedium~size to large businesses that send vast amounts cf data between locations ali over the coumry.

Types of Modems To be "technical1y" correct, a modem

is only the circuitry that convens digital data to tones and vice versa; but over the years l modem has become a generic rerm for the "box" that con~ nects the computcr and phone, no mat~ ter what's added on.

The two types of modems are acouscic couplers and direct-connect modems. An acoustic coupler is a box with rubber cups imo which Vou place the handset of any standard telephone. lntormation is received using a microphone that picks up the cones from the earpiece and is sent out by a tiny speaker [hat uses the mouthpiece .

The biggest advantage of acoustic couplers is low cost. Because they're not connected directly to the telephone !inc, they don't have the special cir~

5wn Mia5rKoII ·s ki 15 a 5cnior lechnlcal editor for Popular Computing.

No\'cmbcr 1952 Popular Comj"lut m~ 19

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cuitrv the telephone companv requires to make an electrical connection to the nationwide telephone svstem. Thev're also convenient to use-just plop the handset into the cups. If VOU traveI with a computer, an acoustic coupler is convenient, especiallv in hotels where vou don't have a telephone jack.

But acoustic couplers have one large disadvantage: the use of extra microphones and speakers increases the chances for distortion and error. The biggest problem is the microphone in a normal telephone, which is not

designed for high-speed transmission of tones. Telephone microphones use car­bon granules, a technologv essentiallv unchanged since Mr. BeU called Mr. Watson. Thev're fine for normal voice transmission, but atter a period of time the carbon granules begin to pack together, resulting' in distortion. The combination of tones used to send data accelerates this process and after a while vou start to get garble on vour video displav. If Vou use an acoustic coupler on a regular basis, you'l have to rap the handset on a hard surface every once in a while to keep the granules "loose." There is a better wav though. Special microphones are avail­able to replace the element in the hand­set and eliminate most problems.

Because of their many advantages, direct-connect modems at:e quick1V becoming the standard wav to tie vour computer to the telephone lines. In­stead of using cups with microphones

and speakers, Vou plug a direct-connect modem right into a standard modular teIephone jack. There's normallv a place to plug in vour telephone also, because that's used for dialing. Feeding and receiving tones direct1v to and from the phone lines is a much more accurate means than using acoustic couplers.

Direct-connect modems cost a bit more than acoustic couplers because they're connected electrically to the telephone svstem. The telephone com­panV is tJery pickV about what it lets Vou connect to the nationwide telephone network and requires direct­connect modems to be certified bV the FCC (Federal Communications Com­mission). Having a modem certified for direct conneetion requires time, monev, and the production of special circuitry bv the manufacturer.

lf Vou have a permanent computer installation, direct-connect modems are also the most conveniente Once vou've plugged everything together, all vou have to do is dial the number, wait for an answering tone, switch on. the modem, and hang up the handset . Direct-connect modems also usuallv take up less space than' ácoustic couplers; they sit under the telephone or eyen plug in inside the computer.

Modems also come in several dif­ferent tvpes of transmission modes. Most designed for personal computer use have a switch with two positions: answer and originate. The terms refer to

the frequency of the tones used to represent the binarv data. Y ou11 prob­ably use the originate mode 99 percent of the time, especiallv if vour main use is hooking up to information utilities and electronic bulletin boards. If )'ou

originate the ca11, that's the position vou use.

lf vour modem has an "answer" posi­tion, vou'll use that if a friend calls and wants to send something from his com­puter to vours. So thar both modems won't be sending the same tones down the line at the same time, one modem is set to "answer," the other to "originate."

Manv modems also have an auto­

answer capability, which is handv if Vou ever want to set up vour own electronic bulletin board or message service. In auto-answer, the modem senses the ringing signal on the telephone line and connects itself. Thus Vou can automati­callv receive messages even if Vou aren't phvsicallv presente (Here at Popular

. Computing, we use a computer with an auto-answer modem to receive stories from our reporters.)

You can save monev bv buVing an originate-onlv modem. The elimination of extra circuitrv lowers the price con­siderablv (some are as low as $100). Btic before Vou do, make sure Vou won'c need the answer or auto-answer cap­abilities.

In the jargon of data communica­tions, other common terms are full duplex and half duplex. Essentiallv, thev represent the difference between a two-

Modem communications. The drawings sbow how modems allow personal computers to communicate. laft: data flows fram one computer through a modem to the telephone lines, to another modem, which converts the audio information to digital form for the receiving computar to use. Right: the two means Df hooldng up to the telephone system are direct-connect and acoustic coupfing.

90 NovembeT 1982 Popular Computing

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way and a one·way conversation. In full duplex, both computers are using the phone line at the same time with data flowing in both directions. It's just like a regular telephone conversation, where two people can· talk at the same time.

Half duplex is like talking on a CB radio -only one computer can send data at a time; the other must wait for the message to end before sending its own.

FuIl duplex is the most commonly used method of communications because it's the most efficient. Some older terminais require half duplex; and if Vou want to use 1200 baud on a voice.grade telephone line, you11 have to use it. (To repeat, the standard voice· grade telephone lines don't have the bandwidth to handle a full.duplex com· puter conversation at 1200 baud.)

It's important to note' that full duplex isn't twice as fast as half duplex. The reason for this is that communicating computers send and receive data asyn· chronously -that is, in a continuously variable start/stop manner. This ran· dom flow of .data means that whether you're operating in fu11 or half duplex, data is never flowing a11 of the time.

Wbat's a 103? T erms like cc 103 compatible" keep

cropping up in modem literature and advertising. This telephone company ·compatibility issue can be a thorny one and more than a bit difficult to under· stand. But, essentiaIly, alI these terms mean is that the scheme by which the modems send out and receive data complies with a standard established by the Bell System. The standard refers mainly to the frequency and length of tones. Basically, there are three types of compatibility: 1. I03/113-full duplex at 300 baud (30

characters a second can be transmit .. ted and received at thesame time in both directions).

2. i02-half duplex at 1200 baud (120 characters a second can be either transmitted or received in one direc .. tion).

3. 212 - fu11 duplex at 1200 baud (120 characters can be transmitted and

92 November 1982 Popular Computing

received at the same time). This complicated standard requires either a conditioned telephone line or two voice.grade lines -one for sending and one for receiving.

When picking a modem, Vou usually don't have to worry about these com .. patibility numbers because alI informa .. tion utilities use the standards. However I if you'lI be swapping data with another personal computer owner, both modems must have the same compatibility number.

The Intelligent Modem A few short years ago, a modem was

a straightforward computer accessory that did two things well: modulate and demodulate. But like other peripherals, modems are becoming intelligent. Manufacturers are adding microproces .. sors to their modems, creating units that automatically dial the telphone and even log on to a database. As 1200 .. baud modems beco me more popular, these "smart" versions will become even more important as the microprocessor takes an active role in controlling the flow of data across the telephone lines.

The Software Question Once you've picked out your modem,

there's still the step of getting the data from the computer to the modem and back again. That's the job of com· munications software (sometimes called tenninal software because it turns your computer into a terminal essentially by "disconnecting" some of the internaI circuitry). Because most modems use the RS-232C connector on the com .. puter, you11 need a means to receive the data and send it out that porto

A wide choice of communications software is available, ranging from basic and inexpensive to sophisticated and costly. In fact, Vou might not have to buy communications software at all because some microcomputer operating systems already have terminal packages buHt in (e.g., CP/M and Radio Shack's TRSDOS).

The cheapest and most basic com· munications software allows data to be sent out the RS·232C connector as vou

type on the keyboard and information received to be displayed on the video screen. Although that's fine if you'll be using data communications only occa· sionally, you11 probably want a few more features. At the least, you11 want to make sure vou have communications software that lets a printer "echo" what's appearing on the video display, allowing Vou to have a hard copy.

Sophisticated communications soft· ware packages turn a personal com· puter into the equivalent of a intelligent terminal by using the computer's microprocessor, memory, and floppy· disk drives. A good package can pay for itself in convenience and savings on long·distance telephone charges. It will alIow vou to save the data Vou get on a disk (for later editing) and even send a file of data on a disk down the phone line alI at once. (Even at 300 baud, sending data you've prepared while ccoff line" is considerably faster than typing it in by hand.)

Features abound on the most expen· sive packages. Some even let vou store the telephone number and log-on se .. quence for a particular database on a floppy disk.

Taking the Plunge Popular Computing has compiled

charts of both modems and com· munications software to help Vou get off and running in telecomputing. Even though alI modems do essentiaIly the same thing, there are Loes. of them around. Differences come in speed, type, special features, and (especially) price. The wide range of prices reflects special features and special circuitry. (The 1200·baud modems require much more sophisticated circuitry than their 300 .. baud cousins; and the circuitry re .. quired by the telephone company to aIlow direct-connect modems to plug into the telephone lines adds to the cost.)

You should study the charts as a starting point for your shopping. Although a modem isn't as "glamorous" a peripheral as a hard-disk drive or a high .. speed printer, it serves an impor· tant role-connecting your computer to the world. O

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Reading the Charts THE MODEM CHART

We've divided the modem chare inco two categories: low-speed modems that can transmit d ata at up to 300 baud and medium-speed modems that can transmit data at up to 1200

Type. Although the term "modem" refers specific alIy to the modulation/ demodulation circuitry, it's used genericalIy to refer to the whole "box." T he two basic types of modems are acousric couplers and direcr­connecr modems. Acoustic couplers use rubber cups in­to which Vou place a telephone handset; direct­connect modems let vou plug the modem into a standard modular telephone jack. Speed. The speed at which a modem transm its and receives data is measured in bps (bits per second), which is commonly referred to as baud. The most common speed for Ac'oustic

baud. High-speed modems also exist but they a re used with large computer systems rather tha n micracomputers . H ere are a few guideli nesfor in­terpreting the information pravided in the charrs:

is needed if vou inte nd to set up your compurer as a bulIetin board system ar want to receive data when you're nor ar the compute r . On auto·answer I the modem senses the telephone ring, connects itself tO the line, and feeds data to your computer. Duplex. Full duple" means th at a "conversation" between two computers can take place with data

modems is 300 baud, rhe de fac to standard for most personal computer communications. It is the maximum speed at which most of the low-cost untcs can transmü: However, as tele~ phone communiC3tions between com·

being reccived ?nd sent at the same time by borh machines (like a normal telephone conversat ion). Half duplex means that o nly one side can send ar receive information ar a time (like ralking o n a CB radio) . Telephone Company Com­patibility. This standard assures that a modem co nforms to re­qu irements established by th e Bell

!!!!!!~;:~:= System for transmi tt ing and te­" modem ceiving data over the telephone

puters becomes more widespread, faster modems­most commonly 1200-baud unirs-are increasingly in demando Many of these faster modems can also operate at 300 bHUd. Transmission Modes. Originare is the mode you'lI need most of the time . lt 's used when Vou make a calI to an "information utility" such as The Source ar Compuserve, or to a computerized bulIetin board system (CBBS) . The answer mode is needed if you'lI be using the telephone lines to communicate with another personal computer user. One of vou wilI need to have your modem set to originate, the other to answer. (Ir won'e marter who uses originate, and who uses answer mode -the importanl~· thing is that the two computers use opposite setti ngs.) Auto-answer

network. In order fo r information to be exchanged, modems on both sides of the lines must have the same compat ibility number: 103/ I I3 refers to opera­tion at 300 baud; 202/ 2 I 2 to 1200-baud operation. Remarks. Modems with special featu res are becom­ing more prevalent. The most common are:

Self-resr-alIows Vou to test your modem/ com­puter/ sorrware instalIation ::'y having tlie modem loop signals through your telephone and computer back to itself.

Auto-dial-lets vou store commonly calIed numbers and automatically dial them by punching a button on the modem a r a key o n the computer.

Compurer-conrrolled dialing - allows vou to type a number on the screen and have the modem dial ie.

NEXT MONTH: COMMUNICATIONS SOFTWARE It t akes more than h ardware to com plete the

data communications package. You must also h ave software to handle communication pro­toco ls, perform d a ta translatio n s, and store and

retrieve received data . Next monch, we' ll presenc a comprehensive charr of communications soft­ware, ranging fram dumb-terminal emulators to full-featured, unanended-operation packages.

A Final Note: The in(ormatio n concained in the modem chart was taken from a variety of sources. A lchough we believe ie to be co rrect and up to date, POPltlar Compwing cannot be heid lia'ble for errors and omissions. \'Ve appreciate n~ader in~ puto Any corrections or additions should be sem to Modem Chart, PO B 397, Hancock. NH 03449.

'4 Novc:mber 1982 Popular Co mpuling

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Datec 32 5250 acowrtic 0-300 origiDat.1 hell 1031 Datec Inc . p~ coupler boud anow.r 113 300 Eut Main SI.

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./ GDC 103J-M $249.95 direct- 0-300 originatel fuII 1031 General DatAeom Industrie. connect boud A.DlIW8r 113 'H above

auto-an.swer

Hayes $219 acou..tic 0-300 oriqin.atel fuII, 103 Hayes Microeomputer Producta me. 17Afb Sma..rtmodeID. coupler boud annrer hell 5835 P&aehtree Coruerl E.ut

autO--an8'Wer Norerou, GA 30092 (.04) 449-8191

Haye, $319 direct- 0-300 originatel full, 103 Haye, Miclocomputer Products Inc . Mieromodem li connect baud .uuwer balf Me above

auto-a..DIW8r

Haye. $399 dírect· 0-300 originatel fuII , 103 Hayes Mic rocompufer Products Inc. for S-lOO-buI Micromodem 100 conneet boud ...... r half ... abov. computen

P\ .. n o:mb.:r !<}d2 Populilr Co.>mpuung t1

' -I

, I • · o~ Co' e . ~ .~, ~o<Q.e.~ .;:. • .s> v-0l> ,~

-.J' • I> "0'1.1>

... ,"" ~" ~ ... .... \.'1.''';9''' ""i &t'f.~ V-,,, ·c· ... i'I' .;:.. <;)'>'1 CO~ç CO~ç ",".~ 'I" -.J'

, V HP 829SO·A $395 clirect· 0·300 oriqi.n.ate' fulJ, 103 Hewlett-Paclcard Co. Seri" 80 eonnect baud an.we, hall lSOI Paq. Mill Rd.

I Palo Alio, CA 94304 i (415) 851-IS01 I I

V lnmoc BOOO SI69 &coustic 0·300 originaie! ftill, 103 Int1 Minicomputer Accesaories Corp.-coupler baud OllrNe, hall 2465 Auqustille P ,.

Santa Cluo, CA 95051

i ' .1 (408) 121·1910

i1 SI15 acoustic 0-300 oriqinAteI fulJ 103 Lu:icon Corpo .t

coupler baud an.w.r 15411fW 65th Av • . !I FI. Lauderdale, n 33313 ' . (305) 192-4400 '; '.

SI95 acoustic 0-300 oriqma.tel fulJ, 103 La:deou Corpo coupler baud .".,..r hall see above

-.,- - ' _. ' ~

>\ MFl·l230 $129.95 inductive 0-300 orlqinatel fulJ, 103 MFJ Enterpril .. Inc. Appl" pluQ' ·!.n coupler baud &DOW., hall 921 LouJ.vill. Rd. v.raiou

Starkville, MS 39159 availabl.

"'::.~J~ . :. ~ . '~ . ..,'. _ _ ..:. .. _. J ............ _,~. (601) 323-5869 (SI39.95)

~ ... ........... > -.' • •• _i __ .. . ~ •• ~

Modlech S216- direcl- 0-300 originat. fulJ 103/ Modlech me. j U"O 101103 S250 connect baud only 113 1958 Hehinld W oy

Livermore, CA 94550 (415) 441-9349

. .... . - .. <-_. ",- " ':." ", . , . ,i Modtech $250 clireet· 0-300 orlqin4lo1 fulJ, 103 Modtech Inc. , MIOJ.C coru>K'I . baud ....... er hall _abov. i .

_. ' •.• . ......-,.4 .,' .~ _ _ ........ ..... .... ......... -", ... ' -~ _.-.... . . - . . _ .~. ;~. { - - -" '-- ',- '-Modlech $316· d.i.rect· 0-300 oriqinat./ fulJ 103/ Modlech Inc. MI03·A $350 connect baud """'., 113 Me above

Modlech $360 clirect· 0-300 oriqinaW fulJ 103 Modlech Inc. MI03A·C connect baud .".,..r _abov.

l: . ~ •. ~ • __ ~ 00-0'- ... , . ,

(8ulti.Tech ! i $225 accuStic 0-300 originate fulJ, 103/ Multi·Tech Syste"" Inc. /'IAT" 1 , 1'10130 coupler baud only hall 113 82 Second A v • . SE ! I New Brighton, MN 55112 II (612) 631·3550

li Multi·Teeh $235 clireet· 0-300 o oriqinat. fulJ, . 103/ Multi·Tech 5111."" , MT113C connect baud cmly hall 113 ... aba ••

Multi·Tech $265 acoudic 0-300 oriqiIlat./ fulJ, 103/ Multi-Tech 5ystem. F).! ·31 coupler baud answ.r hall 113 Me above

Multi-Tech $215 clirocl· 0·300 oriqinate/ fulJ 103/ Multi· Toch System. ata.nd-alcn. MT113D connect baud .".,..r 113 Me above or rad:-mount

auto~er

Multi·Tech $295 d.irect- 0·300 oriqinate/ fulJ 103/ Multi-Tech System. IiAnd-alone MT1031 ccnnect baud .".,..r 113 5e6 abov. cr rack-mount

auto-answer

j Novation $189 acoUltic 0-300 oriqinate/ fulJ, 103 Novation Inc. ,-vt>

c..1 coupler boud .".,. .. hall 18664 O""",d SI. Tar.."., CA 91358 (213) 996-5060

" S O\"mlber 1982 Popular Computing

• • ~ ~e\ ' o~ v

• t;f;' ~. . Õe ~O ~ f>"'<"" ç"ft.0 . ~,,,'i

I • ~O &,- ,I> ,,\1.& ~" ~.~ ,,\e\e .~, ~ .'1-'

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I ovation $189 aeou.st:ie 0-300 oriqinate full. 103/ Novation Inc . Cat Aeoume eoupler baud only hall 113 ... abov. I

Novation SI99 direcl- 0-300 origina le! /UU, 103/ Novation Inc. O-C. t eonnect baud an.swer h.U 113 5&9 above

NovatioIl $249 direct- 0-300 oriqiDalel Juli, 103/ Novation Inc. Auto-Cat eonnect baud an.wer hall 113 Na above

aulo-answer

Novation S340 direct- 0-300 originale full , 103/ Novation Inc . 4100 eonnec t baud only hill 113 Me above

I [

Om.nitec $125 acouatie 0-450 origin.ale full 103 Omnitec nata ,. 715 coupler baud only 2405 50ulh 20th SI. ?1/IJ I

Phoenil:, AZ 8S034 I , (602) 258-8244 ,

i Omnitec SI95 ac:oustic 0-450 oriqinale full . 103 Omnilee Data

I 710 eoupler baud only hall aee above

I

I Omnit.e $225 diroct- 0-300 oriqiDote/ Iull 103 Omnitec Data 91230 connect baud anow.r ... abov.

auto..anJWer

., Omnitee S296 acoustic 0-450 originale! /UU, 103 Omnilec Data m eoupler baud """".r hall Me above

Omnit.e S380 diroct- 1).300 oriqinata! Iull. 103 Omnitec Data automatic 911lB c onnecl: baud anower hall _above dJalinq and

auto-an.war rediaJlnq

. .' .,. --Omnitee $395 acoustic 0-600 oriqinate! Iull, 103 Omnitec Data ava.ilable 776 coupler baud answer hall aee above as a Xii

rentio. $199 acoustíe 0-300 oriqinata! Iull. 103/ Prentice Corp. MU-Iest Il4'V S ter coupler baud anowor hall 113 266 Cupian Or_ Swmyvale, C A 94086 (408) 734-9810

Prentice $385 direct- 0-300 oriqinale full , 103/ Prentiee Corp o P113C COJlllect baud only hall 113 see above

Prentiee $395 diroct- 0-300 auto-annrer Iull, 103/ Prentice Corpo P1130 connect baud only hall 113 ... above

Prentie. $470 direcl- 0-300 oriqinale! full, 103 Prentiee Corp . PI03) eonnect baud an.wer hill see above

autO-ADJWar

Racal· VadJe $250 diroct- ' 0-300 oriqinate! full, 103/ Racal-Vadie Ine. VA317 connect baud anower hall 113 222 Cupian Or_

auto-answer Swmyval., CA 94086 (408) 744-0810

r-:o\'~mb:r 19S2 Porul;r Compuung " i.

• §J- ·cPe\ ' 0<> ~CO '

• .~, :-o.o<Q. .~ .~ y.oÕ· f> ~

e,ç • .l> <"0" ,;' ~.~

<. .\.ç »9'S> ~ e.,.'i--t ' 0· ç' ço" ~&'1.e

'/" <.-{I'. y.oÕ· <;f'ç co~ co~ '<-.~

Racal-V adie $250- direct- 0-300 oriqinalel run, 1031 Racal-V adic Inc. VA 103 S380 connect boud """'er hall 113 Me above

auto-/JJl.IWer

RacaJ· Vadic $375 direct· 0-300 originate! Juli, 103 Recal·Vadic Inc. auto·originate VA315 connecl baud .".,.er h.U 11&8 e.bove optiow

auto·a.nswer

Radio Shacle $149 diroct- 0-300 onqinatel Juli 103 Rad..io Shaclc Modem I connecl boud """".r 1800 Doe Ta..ndy Center

Forl Worth, TX 76102 (817) 390-3011

Radio Shacle S199 acoustic 0·300 origina leI Juli, 103 Radio Shacle Telephone coupler baud an.swer h.U see e.bove Interface D

R.dio Shack $249 direct- 0-300 oriqin.ate! fuIl, 1031 Radio Shack Modemn connecl boud .".,..r halI 113 see ahove

auto--answer

V lUxo. S595 direct· 0-300 onqinate! Juli 1031 Rixon Inc. self·test Tl03J connecl boud .".,.er 113 2120 Industrial Parkw.y

Silver Sprioo, MD '20904 (301) 622-2121

". - --..... - -. ... -_ .~-_ ..

' .. " .. _--.... , ... -".- " . . - . ..." . .. -. . _-_.-~

Tele-Com $195 acoustic 0-300 originate run 1031 Tu·Com Inc. 1# TC3006 coupler boud ooly 113 2142 Paraqan Dr.

San Joee, CA 95131 (408) 263-7400 ........ - .. . ~ - --... - . _ ... _ .... .. ..... "'- - '. '

Tele·Com $249 acoustic 0-300 oriqin.ate Juli 103 Tele·Com Inc. TC3OO1 coupler baud oo1y aee a.hove

Tele-Com S3ôS- direct- 0-300 oriqinalel fuIl, 103 Tek-Com Inc. automatic TC4OO7 $495 CODJl.8Ct boud ."..,..r halI ... abov. dialinq

I · auto-a.n.wer i ., - .. .. - .... . - .. - .. _--_ .. _ .. --- -. -- . -. _-,._,

-i Tuck 1542 $168 direct· 0-300 originate Juli 103 Tucle Eleclrollics Inc.

I -"é?> ; [

connect boud oo1y 3645 Industrial Parle Rd.

iI Camp Hill, PA 17011 , , (717) 761-4354 i' I ' 0 ' - .. _ .. ,.,

,I Tuck 1543 SI68 direct- 0-300 originatef fuIl 103 . TucE E1ectronica Inc. : i connect boud ....... r Me abov. I!

I' , '

I: Tuck 1S30 5297 d..i.rec!· 0-300 origina leI Juli , 1031 Tucle Electron.ic! Inc. automatic connect baud .".,.er halI 113 see above dialinq

! auto-answer

Tuck 1810, $395 direct- 0-300 oriqina.1e haU informa-Tuck ElectroniclI Inc. connect baud oo1y tion aee above

NIA

I

VU .S. Robotics I JÃfJ

SI29 acoustic 0-300 origina le i f\111 , 1031 U.S. Roboticalnc. seU-test

Phon8 Link coupler baud an.swer halI 113 203 North Wahuh, Sulte 1718 Chicago, 1L 60601 (312) 346-5650

J Vea·Tel S245 acourtic 0-300 origwtel Juli, 1031 Ven-TellDc. I""'" ACI03-1,3 coupler boud .".,..r h.U 113 2390 Wahh Ave.

Se..nta Clara, CA 95051 (4Q8) 727·5721

100 S ovembcr 198Z Populu Computing

-----• • •

' 0" CO ' J>O\ . t.~" ".

J><<" ~ .... ' »0 .~\I'.:'i <' '\ e\0'9 ,,"\P'\ . <Q.i ~ .~ <~ "t\& ~~ ..... ~.~ &\'1-"

~&"f: ~\\Ce '\~< ~J>' ~& ~&

",ç" 'J"ç CO<$' Co~ ~.<"

Veu-Tel S230- direct - 0-300 oriqiDatel luJJ 103/ Ven-T.ll..Dc . MD103-1,2 S395 connect ba. d answer 113 Me a.bove

4uto-~er

Ven-Tel S325- direct· 0-300 oriqinale full 103/ Ven-Tellnc. MD103J-1,2 S395 connecl baud only 113 1I&e above

Veu-Tel $484- direct- 0-300 oriqina1e 1uJJ, 103/ Ven-Tellnc. automatic Ml03J-3,4 A.todiel S550 connect ba.d only haH 113 .ee above diAling

I I !

MEDIUM-SPEED MODEMS I I

AM 202LP $295 diroct· 0-1800 oriqinatel ball 202 A.M. Jaequ&rd S~ems I connect ba.d .".,..r 3340 Ocoan Par< Blvd.

I· Santa Monica, CA 90405 (213) 322-8QOO

AM 202S S515 direcl- 1200, oriqinatel hall 202 A.M. JacqUard Sy.teml !

connect 1800 .,..,.or lee above baud

AM 212A 5900 diroct· 0-300, ori.qÚlate luJJ 103/ A.M. Jacqum System. connect 1200 onlj- 113 Me above

ha.d and 212

Asttocom $795 direct- 0-300, oriqinatel 1uJJ, 103/ Astrocom Corporation 212A connect 1200 ....... r hall 113 120 W .... Plato Blvd.

baud auto-an.wer and SI. Paul, MN 55107 212A (612) 227-8651

Comdata $207 direct- 1200 oriqinatel hall 202 Comdata Corpo 33ZE2.22L connect ba.d .,...,..r 7900 North Naqe Ave.

Mortou Greve, IL 60053 (312) ~70-9600

Comdata $434 ~.irect· 1200 oriqinalel ball 202 Comdata Corpo 33=-421 COnDect ba.d an>Wer tee above

Comdata $837 direct- 0-300, oriqinatel 1uJJ, 103 Comdata Corpo T2UA COnDect 1200 ....... r hall and Me a.bove

ba.d auto~er 212

Datec 212 $795 direct- 0-300, oriqinatel 1uJJ, 103/ Datec Inc . COnDect 1200 an-wer hall 113 300 Eost Main SI.

baud autO-llnSWer and Canboro, NC 27510 212 (919) 929-2135

GDC 202-9D $420 direct - 0-300, oriqinatel hall 103 General Datacot:le Induatrias Inc. .. U-telrl connect 1200 aosw.r and One Kennedy Ave.

baud 202 Danb.ry, CT 06810 (203) 797-0711

GDC 212A $880 direct· 0-300, oriqinatel f.ll 113 General Datacom Industriei lelf-talt connect 1200 answer and l&e above

baud 212

Haya. $699 direct- 0-300, oriqinatel 1uJJ, 103/ Haya. M.icrocomputer Produdl Inc. autoMatic

Smartmodem 1200 connect 1200 ."...er ball 113 5835 Peachtree Coroera East dialinqj

baud auto-All8Wer and Norcross, GA 30092 audio 2021212 (404) 449·8791 monitor

NO\leln~t 1952 POj)ular Computinp: 10 t

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' 0<> CO -. ~",\ "e

I>'~ Y.0 '{).,&<$'\ :-e.0 . : • .'"'1

Y.0 !> oI> -t .... b \.~ ~.~ ,\0\e'9 &\~~ -0.-0.1 &",'i-'"

I ~'b'i-e ~,\\Ce '\~. <;çe y.oÕ

e 'O .. ç co'(to'9 Co~ç ~e,"

I Ic.tertel $695 direct· 1200 oriqÚlalel half 202 Intertellnc.

I 1011200 COllllect baud a=we, 6 Sh.ttuck Rd_

Andova!, MA 01810

I , (617) 681-0600

Modtech $850 direct- 0-300, onC]mals! full 103 Modtech Inc .

I M21ZA connect 1200 answer AIld 1956 HeI.inld W.y baud 212 Livermore , CA 94550

(415) 447-9349

Multi-Tech $695 direct· 1200 oriqinatel full 212A Multi-Tech Sya1emslnc. atand-alone MT212D connect baud onswo, 82 Second Ave. SE or rad:-mount ., auto-AllIWer Naw Briqhton. MN 55112

(612) 631-3550

Multi-Tech $850 cWecl- 0-300, originais! fuli 103/ Multi-Tech System! rtand-alone MT212A cOllJl8cl 1200 answar 113 5ee above ar rack·mounl

baud 4uto-a.nswer AIld 21ZA

, I NOY4tion 4200 $375 direct- 1200 originalsl holl 202 Novation Inc. I

COtulect baud anBWe< 18664 Oxn."d SI. auto-answer Tarun4, CA 91356

(213) 996·5060

Novation $389 direct- 0-300, origina le I full, 103 Novation for the Apple Apple·Cat fi connect 1200 answe, half and see above n on.ly; auto-

baud aulo-,uuwer 202 matic dialinq

Novation $895 efuect- 0-300, orlqin.ate l full, 103 NovatioD. Inc. automatic 2l2Auto·Cat COlJllect 1200 .".,.e, half and 188 above dialinq

baud auto-an.wer 212

NovatioIl $725 direct- 1200 oriqinatel full 212 Novation Inc. automatic 212 Appl.·C.t connect haud answ., s&e ahove dialinq;

auto-a.nswer priDter interlace

Omnitec 9202B SS45 direct- 1200 auto-a..nswer full, 202 Omnitec Data automatic ,-I eoD.llect baud only ' holl 2405 50ulh 20th SI. dialinq and " I ' Phoenil:, A2 85034 rediali.nq , I

(602) 256-8244 , , " , i Omnilec $785 direct- 0-300, orlqinatel full 103 Omnitec Data automat:inq , . j: 9212AOO connecl 1200 answe' and see above dialinq ., baud aulo-answar 212 and redialinq I' I I i i Penril $550 direct- 1200 oriqinatel half 202 PanrU Corpo

I: 202 AVO COD.llect baud answe, 3204 Monroe St. Roclcville, MO 20852

I (301) 984·8225

Penril S850 direct- 0-300, oriqinalel full, 103 Penrü Corp o seU-test 300/1200 connect 1200 answer holl and see above

baud auto-answer 212

Ptentice 212A S795 direct- 0-300, oriqinatel full, 103/ Ptentice Corpo connect 1200 answa< half 113 266 c..pi4n DL

baud aulo-4IlSWet and SWlllyvole, CA 94086 212 (408) 734-9810

Prentice 212C $795 direct- 0-300, oriqinatel fuli, 103/ Prentice Corpo self-Iest connect 1200 answer holl 113 aee ahove

baud aulo-answer and 212

&leal·Vadie $400 direct- 1200 originalel half 202 RecaI-Vadie Inc. VAI224/45 connect baud answer 222 Caapi411 Dr .

SWlllyvole, CA 94086 (~08) 744-0810

101 S .:wem:-..:r i "~; Pupular C"'nlPUUnil

'í·' • ~ , '" ..

óo\ ' 0" CO ' .... ~\ ~.

êe~ ",,:\0 ~~«$J>\ :tl-0 . ~\ ... i ,,"0 1> .ó .,,\:~& )...~" ~.~

-t e\e9 -\9' :oi &\'f..o; : i &\ &"'ól-.,p.1>'i-

e "'t~,Ce ",{lO "'~. ,,"OÓ' '\Jv~ CO~9 CO~9 ~.<$'

', i Racal· V adic $425 direct· 1200 origina te! hall 202 RAcal· V adie Inc. . 1 1250/55 connect baud anawer Me above ,

auto-answer

Racal · Vodic 5525 direcl· 1200 originalel hall 202 Rocal·Vodic Inc.

I VA1251 /52 connect baud answer see obove I., I 'I ' ' . i Rad..io Shock 5699 direct- 0-300, originate! /UU, 103/ Radio Shack aulomatic

,I DC-12OO connect 1200 ...... er hall 113 1800 One Ta..ndy Cenler clialiDg;

'! baud auto-anawer .. d Forlh Worlh, TX 76102 aelI-test 2021212 (817) 390-3011

Rixo. TA-212 5795 direct· 0-300, originate! luU 103/ Ri:J:on Inc . connect 1200 answer 113 2120 Industrial Parkway

baud auto-answer .. d Silver Sprinq, MO 20904 212 (301) 622-2121

Rixo. T212A $895 direct- 0-300, originate! luU 1031 RU.:on Inc . seil-Iem connect 1200 ....... r 113 Me above

baud auto-answer .. d 212

Telr.-Com 5849- acou.stic 0-300, originale! 1uU, 1031 T.k-Com Inc. TC2122A 5995 coupler 1200 an.swer hall 113 2142 Paragon Dr .

baud auto-answer and 5 .. lo •• , CA 95131 212 (408) 263-7400

Tue'163O $235 direet- 1200 originaie haIl 202 Tuck Eleclronica Inc . connact baud only 3645 Induotria.l Par. Rd _

Camp Hill, PA 17011 (717) 761-1354

Tue'1650 5242 direct· 1200 originate haIl 202 Tuck Electronicl connect baud only Me above

Tud: 1563 $275 direct- 1200 oriqinaLe haIl 202 Tuclr. ElectronicI connect baud only _abov.

i 5375 dUocl- 1200 haIl 202 Tuck Electronics ji Tue' 1610 original.

connect baud only Me &bove

I' li

Universal Data $495 d.irect· 1200 originatel luU 212 Universal Data S}":teml Syst. "" 212LP connect baud ....... r 5000 Bradford or.

Huntsvill., Al 35805 (205) 837-8100

Universal Data 5695 direct· 0-300, oriQinatet full 103 Universal Data 5ysteml 5ysteml 212LP connect 1200 AIlIWer and 1&8 above

baud 212

U .5 . Robotic:s 5549 direct- 1200 origiDa!el luU 212 U.5 . Robotics Inc . ..lI-lerl M;ero !.in. 1200 connect baud an.ower 203 Norlh Wa.b.,h, Sul'. 1718

ChicaQo, n. 60601 (312) 346-5850

Ven·Tel $850- direct· 0-300, oriQiDatet full, 1031 Ven·Tellnc. MD212·I,2 $995 connecl 1200 answer hall 113 2390 Walsh A v • .

baud 4uto-4ll5Wer .. d S411ta Clara, CA 95051 212 (408) 727-5721

Ven·Tel $925- Wrect- 0-300, originate 1uU, 1031 Ven·Tel Inc. automatic MD212-3,4 $995 connect 1200 only haIl 113 Me above dialiDq Au'odial baud and

202/212

104 ~"" t"mb.: r 1 \J ~2 l'''pul:.r Lumpucu11i