Radio Shack TRS-80 Installation manual

SERVICE POLICY
Radio Shack's nationwide network of service facilities provides quick, conven-
ient, and reliable repair services for all of its computer products, in most in-
stances. Warranty service will be performed in accordance with Radio Shack's
Limited Warranty. Non-warranty service will be provided at reasonable parts
and labor costs.
Because of the sensitivity of computer equipment, and the problems which can
result from improper servicing, the following limitations also apply to the ser-
vices offered by Radio Shack:
1
.
If any of the warranty seals on any Radio Shack computer products are bro-
ken. Radio Shack reserves the right to refuse to service the equipment or to
void any remaining warranty on the equipment.
2. If any Radio Shack computer equipment has been modified so that it is not
within manufacturer's specifications, including, but not limited to, the in-
stallation of any non-Radio Shack parts, components, or replacement
boards, then Radio Shack reserves the right to refuse to service the equip-
ment, void any remaining warranty, remove and replace any non-Radio
Shack part found in the equipment, and perform whatever modifications are
necessary to return the equipment to original factory manufacturer's
specifications.
3. The cost for the labor and parts required to return the Radio Shack com-
puter equipment to original manufacturer's specifications will be charged to
the customer in addition to the normal repair charge.

Wad
TERMS AND CONDITIONS OF SALE AND LICENSE OF RADIO SHACK COMPUTER EQUIPMENT AND SOFTWARE
PURCHASED FROM ARADIO SHACK COMPANY-OWNED COMPUTER CENTER, RETAIL STORE OR FROM A
RADIO SHACK FRANCHISEE OR DEALER AT ITS AUTHORIZED LOCATION
$m
CUSTOMER OBLIGATIONS LIMITED WARRANTY
A. CUSTOMER assumes full responsibility that this Radio Shack computer hardware purchased (the "Equipment"), and any copies of Radio
Shack software included with the Equipment or licensed separately (the "Software") meets the specifications, capacity, capabilities
versatility, and other requirements of CUSTOMER
BCUSTOMER assumes full responsibility for the condition and effectiveness of the operating environment in which the Equipment and Software
are to function, and for its installation
II. RADIO SHACK LIMITED WARRANTIES AND CONDITIONS OF SALE
AFor aperiod of ninety (90) calendar days from the date of the Radio Shack sales document received upon purchase of the Equipment, RADIO
SHACK warrants to the original CUSTOMER that the Equipment and the medium upon which the Software is stored is free from manufacturing
defects THIS WARRANTY IS ONLY APPLICABLE TO PURCHASES OF RADIO SHACK EQUIPMENT BY THE ORIGINAL CUSTOMER FROM
RADIO SHACK COMPANY-OWNED COMPUTER CENTERS, RETAIL STORES AND FROM RADIO SHACK FRANCHISEES AND DEALERS AT ITS
AUTHORIZED LOCATION The warranty is void if the Equipment's case or cabinet has been opened, or if the Equipment or Software has been
subjected to improper or abnormal use If amanufacturing defect is discovered during the stated warranty period, the defective Equipment
must be returned to aRadio Shack Computer Center, aRadio Shack retail store, participating Radio Shack franchisee or Radio Shack dealer
for repair, along with acopy of the sales document or lease agreement The original CUSTOMER'S sole and exclusive remedy in the event of
adefect is limited to the correction of the defect by repair, replacement, or refund of the purchase price, at RADIO SHACK'S election and sole
expense. RADIO SHACK has no obligation to replace or repair expendable items
BRADIO SHACK makes no warranty as to the design, capability, capacity, or suitability for use of the Software, except as provided in this
paragraph Software is licensed on an "AS IS" basis, without warranty. The original CUSTOMER'S exclusive remedy, in the event of a
Software manufacturing defect, is its repair or replacement within thirty (30) calendar days of the date of the Radio Shack sales document
received upon license of the Software The defective Software shall be returned to aRadio Shack Computer Center, aRadio Shack retail store
participating Radio Shack franchisee or Radio Shack dealer along with the sales document
CExcept as provided herein no employee, agent, franchisee, dealer or other person is authorized to give any warranties of any nature on behalf
of RADIO SHACK
DExcept as provided herein, RADIO SHACK MAKES NO WARRANTIES, INCLUDING WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A
PARTICULAR PURPOSE.
ESome states do not allow limitations on how long an implied warranty lasts, so the above limitation(s) may not apply to CUSTOMER
III. LIMITATION OF LIABILITY
AEXCEPT AS PROVIDED HEREIN, RADIO SHACK SHALL HAVE NO LIABILITY OR RESPONSIBILITY TO CUSTOMER OR ANY OTHER PERSON
OR ENTITY WITH RESPECT TO ANY LIABILITY, LOSS OR DAMAGE CAUSED OR ALLEGED TO BE CAUSED DIRECTLY OR INDIRECTLY BY
"EQUIPMENT" OR "SOFTWARE" SOLD, LEASED, LICENSED OR FURNISHED BY RADIO SHACK, INCLUDING, BUT NOT LIMITED TO ANY
INTERRUPTION OF SERVICE, LOSS OF BUSINESS OR ANTICIPATORY PROFITS OR CONSEQUENTIAL DAMAGES RESULTING FROM THE
USE OR OPERATION OF THE "EQUIPMENT" OR "SOFTWARE". IN NO EVENT SHALL RADIO SHACK BE LIABLE FOR LOSS OF PROFITS OR
ANY INDIRECT, SPECIAL, OR CONSEQUENTIAL DAMAGES ARISING OUT OF ANY BREACH OF THIS WARRANTY OR IN ANY MANNER
ARISING OUT OF OR CONNECTED WITH THE SALE, LEASE, LICENSE, USE OR ANTICIPATED USE OF THE "EQUIPMENT" OR "SOFTWARE"
NOTWITHSTANDING THE ABOVE LIMITATIONS AND WARRANTIES, RADIO SHACK'S LIABILITY HEREUNDER FOR DAMAGES INCURRED BY
CUSTOMER OR OTHERS SHALL NOT EXCEED THE AMOUNT PAID BY CUSTOMER FOR THE PARTICULAR "EQUIPMENT" OR "SOFTWARE-
INVOLVED.
BRADIO SHACK shall not be liable for any damages caused by delay in delivering or furnishing Equipment and/or Software
CNo action arising out of any claimed breach of this Warranty or transactions under this Warranty may be brought more than two (2) years
after the cause of action has accrued or more than four (4) years after the date of the Radio Shack sales document for the Equipment or
Software, whichever first occurs
DSome states do not allow the limitation or exclusion of incidental or consequential damages, so the above limitation(s) or exclusion(s) mav
not apply to CUSTOMER
IV. RADIO SHACK SOFTWARE LICENSE
RADIO SHACK grants to CUSTOMER anon-exclusive, paid-up license to use the RADIO SHACK Software on one computer, subject to the followinq
provisions:
AExcept as otherwise provided in this Software License, applicable copyright laws shall apply to the Software.
B. Title to the medium on which the Software is recorded (cassette and/or diskette) or stored (ROM) is transferred to CUSTOMER but not title to
the Software
CCUSTOMER may use Software on one host computer and access that Software through one or more terminals if the Software permits this
function.
DCUSTOMER shall not use, make, manufacture, or reproduce copies of Software except for use on one computer and as is specifically
provided in this Software License Customer is expressly prohibited from disassembling the Software
ECUSTOMER is permitted to make additional copies of the Software only for backup or archival purposes or if additional copies are required in
the operation of one computer with the Software, but only to the extent the Software allows abackup copy to be made However for
TRSDOS Software, CUSTOMER is permitted to make alimited number of additional copies for CUSTOMER'S own use
F, CUSTOMER may resell or distribute unmodified copies of the Software provided CUSTOMER has purchased one copy of the Software for each
one sold or distributed. The provisions of this Software License shall also be applicable to third parties receiving copies of the Software from
CUSTOMER
G. All copyright notices shall be retained on all copies of the Software
V. APPLICABILITY OF WARRANTY
AThe terms and conditions of this Warranty are applicable as between RADIO SHACK and CUSTOMER to either asale of the Equipment and/or
Software License to CUSTOMER or to atransaction whereby RADIO SHACK sells or conveys such Equipment to athird party for lease to
CUSTOMER
B. The limitations of liability and Warranty provisions herein shall inure to the benefit of RADIO SHACK, the author, owner and/or licensor of the
Software and any manufacturer of the Equipment sold by RADIO SHACK
VI. STATE LAW RIGHTS
The warranties granted herein give the original CUSTOMER specific legal rights, and the original CUSTOMER may have other rights which vary
from state to state
Mm

Important Note
Before connecting your Modem II to the phone lines, nofity your local
telephone company of the:
Manufacturer: Radio Shack
Model: Modem II, #26-1 173
USOC Number: RJ11C
FCC Number: AA088U-6861 6-DM-E
Ringer Equivalence Number (REN): 0.7B
You can also find this information on the bottom of your modem.
Do not connect your Modem II to:
ID Party-line phones
[x] Coin-operated phones
TRS-80® Modem II Operation Manual ©1982 Tandy Corporation, Fort Worth, Texas 76102
U.S.A. All Rights Reserved.
Reproduction or use, without express written permission from Tandy Corporation, of any portion
ofthis manual is prohibited. While reasonable efforts have been taken in the preparation of this
manual to assure its accuracy, Tandy Corporation assumes no liability resulting from any errors or
omissions in this manual, or from the use of the information obtained herein.

Contents
Introduction 1
1/Description of the Modem II 3
2/Setting Up the Modem II 5
Connecting the Modem II to aTelephone
Connecting the Modem II to aPower Supply
Connecting the Modem II to aComputer
3/Using the Modem II with Videotex Software 9
4/Technical and Programming Information 15
5/Troubleshooting and Maintenance ..23
Test Mode
6/Specifications 25
Appendix A/How Quickly Does the Modem II Dial? 27
Appendix B/Modem II Programming Commands 29
Appendix C/Operational Flow Chart 31

'
'v
Notes

Introduction
With aTRS-80® Modem II your computer or data terminal can communicate with other
computers or terminals via ordinary telephone lines.
The Modem II was designed to work with any TRS-80 computer or data terminal that has
RS-232-C capabilities. This includes TRS-80:
•Model I
®Model II
•Model III
•Model 16
•Color Computer
•DT-1 Data Terminal
You'll need some software —any program containing RS-232 drivers and receivers will work.
Your local Radio Shack Computer Store has several suitable programs, such as Videotex,
Terminal, and the Color Computer Videotex Program Pak.

Note*

1/Description of the Modem
Figure 1. Modem II (Top View)
©POWER Switch turns your Modem ON or OFF. Be sure to turn your Modem OFF when
you're not using it.
©MODE Switches selects four modes of operation: AUTO ANswer, AUTO ORIGinate,
MANual ANSwer, and MANual ORIGinate.
®TEST Switch selects LOCal Test Mode, REMote Test Mode, or turns Test Made OFF.
©ON (Power) Light is on when power in ON.
©OH (Off-Hook) Light is on when your Modem has control of the phone line.
©TR (Terminal Ready) Light is on when the RS-232 control line, DTR (Data Terminal
Ready), is on.
®CD (Carrier Detect) Light is on while your Modem is receiving a"carrier tone."
©TD (Transmit Data) Light flashes when your Modem is transmitting information.
®RD (Received Data) Light flashes when your Modem is receiving information.

•yias^g-ggfr^gsffy< »^Mi'XSi.S^MZS!£i, W5^?''';'*«^«JC^'Z^^fe^'..--feA.«^p
Figure 2. Modem 11 (Rear View)
©RS-232-C Standard DB-25 jack for connection to RS-232-C Interface of TRS-80 Models I,
II, and III, and 16.
©RS-232 Four-pin DIN jack for connection to the Serial I/O (RS-232) of the TRS-80 Color
Computer.
©PWE Jack for the AC adapter plug.
©PHONE Jack for modular-type telephone line cords.
©FORCE DTR Switch forces Data Terminal Ready (DTR) and Carrier Detect (CD) on.
When using aColor Computer, set this switch to ON. When using other computers, the
setting of this switch depends upon how you program your Modem.

2/Setting Up the Modem II
Set your Modem's POWER Switch to OFF before connecting anything!
There are three steps to setting up your modem. Each step is fully explained in this section.
•Connect your Modem II to your telephone.
•Connect your Modem II to apower supply.
®Connect your Modem II to acomputer.
Connecting the Telephone to the Modem II
The way you connect the Modem II to atelephone depends on how your telephone is connected
to the wall. The following three figures illustrate these connections.
If you're using your Modem II outside the USA, you may need aModular-to-Modular Cable
(Radio Shack Catalog Number 279-374) and aDuplex Modular Jack (279-357).
Figure 3. Modular Connector
If your telephone has this type of connection, attach your Modem II as shown. (If you plan on
using the Modem in AUTOmatic Modes only, you don't need to use atelephone.)

==j
Figure 4. Four-Prong Connector
If your telephone has the older style, four-prong connection, use an adapter (279-360) to connect
it to your Modern II as shown.
Figure 5. Wall Connector
If your telephone is wired directly to the wall, contact your telephone company.
Connecting the Modem 11 to Multi-Line
Telephones
You can use your Modem II with amulti-line telephone. However, you may need aMulti-Line
Adaptor (such as Radio Shack Catalog Number 43-270/271 ), ahardware modification to the
Modem II, or both.
If you use aMulti-Line Adaptor only, the HOLD Button on an extension phone can interfere with
communication if someone presses it. To avoid this problem, have aqualified Radio Shack Service
Technician modify the Modem II.
For other Adaptors which may be used, contact your Radio Shack store

Connecting the Power Supply to the Modem II
Insert the AC adapter into the AC Power jack on the back of the modem. Plug the adapter into an
electrical wall outlet.
Use the supplied, UL-listed adapter only. The use of any other adapter could damage the
modem.
Connecting the Computer to the Modem II
The Computer you connect to the Modem II must have RS-232-C capabilities.
Table 1summarizes the cable and connection requirements for RS-232-C equipped TRS-80's.
Table 2provides quick instructions on RS-232-C connection points on TRS-80 computers. For
more detailed instructions, see your Computer's owner's manual.
Modem-to-Computer Cables
TRS-80 Cable Catalog #
Model I
Model 11/16
Model lll/DT-1
Color Computer
26-1145*
26-4403
26-1408
26-3014
Table 1
*The Model IRS-232-C cable is supplied with the RS-232-C Interface
Board (26-1 145). See your Radio Shack Computer Center for details.
Computer RS-232-C Location
TRS-80 Location
Model I
Model ll'16
Model III DT-1
Color Computer
Front of the Expansion Interface
Rear of the Computer
Underneath the Computer
Rear of the Computer
Table 2
To connect the Modem II to the Computer:
1
.
Be sure the Computer and modem's power are OFF.
2. Plug the appropriate end of the connecting cable into the modem's RS-232 jack.
3. Plug the other end of the cable into the Computer's RS-232-C jack.
4. Power up the System as described in your Computer's owner's manual.

•When you're not using the Modem, turn it OFF! If you don't, you won't be able to use your
telephone for normal conversation.
oWhen you use your Modem for the first time or when you seem to be getting garbled data, use
the Modem's two test Modes —REMote and LOCal —to help you find the cause of the
problem.
• Be sure to always sign-off when communications are finished. The sign-off message depends
on the computer that receives the phone call —BYE or GOODBYE are commonly used.
•Because of apre-set feature of the Modem II, the phone will ring twice in Automatic Mode.
To change the number of rings, aRadio Shack Service Technician can modify the Modem
II.
Note to Color Computer Users: Always set your Modem's FORCE DTR Switch ON.

3/Using the Modem II with Videotex
Software
AModem that is connected to aComputer running aTRS-80 Videotex software package
constitutes one of the most common (and exciting!) ways to use your Modem II. This section
will describe how to use the Modem II with VIDTEX (the Videotex program) on TRS-80 Model
I, II, III, and Color Computers.
If you're interested in writing your own programs for the Modem II, refer to the section of this
manual entitled Technical and Programming Information. It will give you adetailed account
of how the Modem II works but on atechnical level.
Manual vs* Automatic Operation
If you want to dial an information service (such as CompuServe or Dow Jones) or communicate
with another person whose computer is also using VIDTEX, you can set the appropriate MODE
Switch to MAN (manual). In this mode, you control what the System does by "manually"
dialing and answering the phone.
If you want the modem to dial aphone number (or answer the phone) for you, set the appropriate
MODE Switch to AUTO (automatic). In this mode, the Modem dials the phone number you
specify or answers the phone when someone calls you. Automatic Mode, for instance, lets you
dial the information service number without picking up the phone —just type the number (along
with the proper Modem II programming commands) on the Computer keyboard. (In other words,
let your fingers do the walking —but on the keyboard instead of the telephone!)
Originate vs Answer Modes
If you want to place acall (to an information service or another person using VIDTEX), set the
other MODE Switch to ORIGinate. In this mode, the call "originates" from your computer.
If you want to receive acall (e.g., "answer" the phone), set the appropriate MODE Switch to
ANSwer.
Note that Originate and Answer Modes can be used either manually or automatically. That is,
you can set the MODE Switches to MAN/ORIG, MAN/ANS, AUTO/ORIG, or AUTO/ANS
depending on your particular needs.
During communication, you can also change the MODE Switch settings without interfering with
communications. When you disconnect from the information service, however, the Modem will
automatically go to the "new" mode. For example, if the MODE Switches are set to
MAN/ORIG (the most common setting when communicating with an information service) and
you want to switch to AUTO/ANS on disconnect, just change the settings before you sign off.
The Modem II will begin waiting for acall and automatically answer the phone after it
disconnects from the service.
If you set the TEST Switch to REMote while communicating with an information service, the
Modem will simulate half-duplex communication and the Host system may send you
1'double-characters .'
'

Videotex and the Modem 11
Videotex software packages that allow you to communicate with an information service or with
other Videotex users over the phone, are available for TRS-80 Models I, II, III, and Color
Computers. For specific details on using an information service once you've established
communications, refer to your information service user's guide.
Color Computer users should always remember to set the FORCE DTR Switch to ON. We
suggest that other TRS-80 users also keep the FORCE DTR set to ON unless your program
explicitly calls for FORCE DTR to be OFF.
MANeal/QRlGInate Operation
The most common (and probably the easiest) method of calling an information service is when
the MODE Switches are set to MANual and ORIGinate.
In this mode, you'll need to be next to the Modem and Computer when you are using Videotex
(e.g., "attended use"). Once the program is loaded, you must dial the information service and
begin communication.
To use the Modem II in MANual/ORIGinate Mode, follow these steps:
1
.
Set the FORCE DTR Switch (on the back of the modem) to ON.
2. Be sure the switches on the front of the modem are set to the following:
r
POWER
\»
mi aNs
\J
\
oooooo
ON OH TH CD TO nD J
f^~\ REIVI
v_/
OFF
LDCJ
3. Load the VIDTEX program as described in your Videotex User's Guide.
4. Pick up the telephone receiver and dial the information service phone number.
5. When the information service answers the phone, you will hear ahigh-pitched tone.
6. Set the Modem's POWER Switch to ON. The RD light will then come on.
Next, the CD light will illuminate and, after atwo second delay, the RD light will go off.
At the same time, you'll hear alow-pitch tone.
7. Gently hang up the phone.
You can then begin following the instructions detailed in your Videotex and information service
user's guide.
10

MANual/ANSwer Mode
If you wish to use VIDTEX to communicate with another person who is also using VIDTEX and
aModem II, one of you will have to set the MODE Switches to MAN and OR1G
(Manual/Originate Mode) and the other person will have to set the switch to MAN and ANS
(Manual/Answer Mode). Although it is up to you and the person you're communicating with to
decide who is to be ORIG and who is to be ANS, we suggest the following sequence:
1. Be sure the FORCE DTR Switch on both Modem II's are set to ON.
2. Both you and the other person should load VIDTEX.
3. The other person should set the Modem II switches to:
_,
o o
ON OH TR CD TD RD
POWER
IN A
PHI
o
/^~\
4. You should set your Modem II switches to:
POWER
v:
ni•^j
5. You should dial the other person's phone number.
6. When the other person 'sphone rings, he/she should pick up the receiver.
7. The other person should set the Modem POWER Switch to ON.
Then both of you will hear ahigh-pitched tone and the Modem's RD lights will come on.
8. Next you should set your Modem's POWER Switch to ON.
Both CD lights will illuminate and, after a2second delay, the RD lights will go off.
At the same time, you both will hear alow-pitch tone.
9. Both you and the other person should gently hang up the phones.
You can then begin communicating with the other person simply by typing on your computer's
keyboards. Your messages will be displayed on the other person's Screen and vice versa. If you
wish to see what you type displayed on your Screen (and vice versa), set your Modem's Test
Switch to REM. If the other person also sets his/her Modem's Test Switch to REM, you will not
be able to communicate. Remember! Only one REMote Test Switch on at atime!
11

Automatic Mode
Automatic Mode Operation allows you to leave your Modem and Computer "unattended" and
the Modem II will automatically dial or answer the phone.
This is useful for many reasons, foremost among them being the Modem II automatically can
dial numbers at night when the phone rates are cheaper, transfer information to another
computer, and then hang-up the phone.
The Modem II has both AUTO/ANSwer (for answering) and AUTO/ORIGinate (for dialing).
AUTO/ANSwer Mode Operation
AUTO/ANSwer Mode can be used in conjunction with MANual dialing or AUTOmatic dialing.
For example, if you and another person wish to communicate using VIDTEX and you've
previously decided on who will be ORIGinating the call and who will be ANSwering it, you may
want to use AUTO/ANS.
In the following example, you will AUTO/ANSwer the phone; the other person will MANually
ORIGinate (dial) the phone.
To use AUTO/ANS:
1. Be sure both Modem IPs FORCE DTR Switches are set to ON.
2. The other person should set his/her Modem Switches to:
r
S~~\
*^-^— ___«_
ooooo •
ON OH TR CD TD "° J
pa WER MOOE TES
K
*^
"\
HEM
QFF
LOCJ
3. Set your Modem switches to:
r~
ff "'•'
o
1ON
%-
o
OH o
TR o
CD o
TD o
RD J
., „
—
-&
KO
v_y
QA,MS
\__y
TEST
f~\ REM
(Be sure your POWER Switch is set to ON!)
4. The other person should dial your phone number. When your phone rings, do not pick up the
received. After one or two rings, the Modem should seize the phone lines (and ON, OH, and
TR Lights should go ON).
12

5. When the other person hears the high-pitched tone, he/she should set the Modem II POWER
Switch to ON.
6. When the other person hears a low-pitch tone, he/she should hang-up the phone.
You can then begin communicating with each other by typing on your computer's keyboards.
AUTO/ORIGinate Mode Operation
Automatic dialing requires that you use programs that have drivers and receivers or write your
own program to dial aphone number. Programs that successfully fulfill your needs can
sometimes become quite complicated. If you want to write AUTO/ORIGinate programs,
carefully read the section of this manual entitled Technical and Programming Information and
refer to the Appendixes.
To use the Modem II in AUTO/ORIGinate Mode under VIDTEX:
1
.
Set the Modem's FORCE DTR Switch to ON.
2. Enter programming mode (send an *). The TR Light will illuminate and the *will echo on the
Screen,
3
.
Type aModem command and phone number. Press Xto dial the number.
4. Begin communications when the CD Light comes ON.
The Modem II remembers program data until you change modes or turn the POWER OFF.
Hints and Tips on Automatic Operation ...
•The Modem II always checks the front panel switch settings on power-up and after a
disconnect.
•Test Mode (when the TEST Switch is set to either LOCal or REMote) has priority over all
other switches. That is if you set the MODE Switches and then the TEST Switch, the Modem
II will always run the Test.
•If you program the Modem in Automatic Mode, the software commands will "override" the
front panel switches only once. After that first override, the action of the Modem will be
based on the switch settings. To override again, you must go into programming mode and
re-execute the Modem II program.
9You can change the switch settings during communications without interruption. However, if
you set the TEST Switch to REMote, the Modem will simulate half-duplex and (if the Host
isn't using half-duplex) your Video Screen will display double-characters. If you are
communicating with another person and both of you set the TEST Switch to REM,
communication will end.
See Technical and Programming Information and Appendix Bfor details on "unattended
use" of the Modem II.
Simulating Half-Duplex
To simulate half-duplex mode, set the Test Switch to REM after making contact with another
computer. If your display shows two characters for every character you type, you should not be
simulating half duplex —set your TEST Switch to OFF and proceed as usual.
13

^M^^*™™™^"^^^'™
Notes
14