Radio Shack Telephone Interface II User manual

This manual provides installation and operating instructions for the
Radio Shack TRS-80 TELEPHONE INTERFACE II. The TELEPHONE
INTERFACE II is used with aTRS-80 Microcomputer System to allow
communications over telephone lines.
The TELEPHONE INTERFACE II is astand-alone, acoustically
coupled, FSK (Frequency Shift Keying) modem. This device forms an
interface between your TRS-80 and the telephone line. The word
modem stands for modulator"modulator. Amodulator is necessary
to convert
the data you type in on your Computer into audio-type signals
which can be sent over
the phone lines. When the audio-type signal is
received at the other end
of the phone line, the modem demodulates
(converts) the signals back into digital data. Your modem is designed to
operate at rates up
to 300 baud on the dial-up telephone network.
(Communication speed is measured in baud, which represents the
number
of signal units per second.)
The TELEPHONE INTERFACE II offers standard features such as
Anlwer and OJiaiDate operating modes. When the modem is in the
OriliDate mode, you are the party to begin all "conversations" with the
remote terminal. When the modem is in the Answer mode,
the remote
terminal starts
or originates the conversation.
The modem provides for communication to proceed in either
of two
different ways: Half-Duplex Mode
or Full-Duplex Mode.
Full-Duplex means that characters typed
on the keyboard are sent
out
of the Computer and do not appear on the Video Displey and/or
Printer.
Half-Duplex means that characters typed on the keyboard are not
only sent out, but appear on the Video Display and/or Printer.
Aspecial TEST mode is built into your modem so you can be sure it is
functioning correctly.
For communications between computers and computer-related
equipment, the most wide-spread and universal standard is the EIA
RS-232-C. This standardized method was adopted by the Electronic
Industries Association to insure uniformity
of interface between data
communication equipment and data processing terminal equipment The
TELEPHONE INTERFACE II is designed for operation with an EIA
RS-232-C Interface, such as Radio Shack's 26-1145.
The TELEPHONE INTERFACE II is powered from aUL-Iisted AC
Adapter.
It provides asource of low voltage AC, thus eliminating
hazardous high voltages inside
the unit.
(Note: The TELEPHONE INTERFACE II is compatible with the Bell
I03A Modem.)
©Copyright 1978 by Radio Shack, ADivision o/Tandy Corporation, Fort Worth. TX 76102
2

SPECIFICATIONS
Receive Frequencies Originate
Mark:
Space:
Answer
Mark:
Space:
Transmitter Frequencies Originate
Mark:
Space:
Answer
Mark:
Space:
Receive Sensitivity -45 dBm
2225 Hz
2025 Hz
1270 Hz
1070 Hz
1270 Hz
1070 Hz
2225 Hz
2025 Hz
Temperature Operating environment: 32-122° F
(0-500 C)
Storage: -40-1400 F (-40-600 C)
Humidity Operating environment: 10-90%
relative humidity (no
condensation)
Storage:
5-95% (no condensation)
Electrical
Requirements 24 Volts AC, 150 rnA, supplied
by UL-listed AC Adapter, with
6' cord
Size 2.3"x 4.7"xlO.2" (HWD)
(5.8 x
12 x26 cm)
Weight 1.5 Ibs (0.68 kg)
3

Controls and Indicators
OATA I/O CO~CTO.
.... I". ~ICCDI""' ••
'"""'""""""1/'''1/'' "1/ "'''1/1/'
Acoustic Coupler for Phone Earpiece-Telephone handset must be
placed so earpiece is pressed firmly into this rubber cushion.
Acoustic Coupler for Phone Mouthpiece-Telephone handset must be
placed so mouthpiece is pressed firmly into this rubber cushion.
Note: The Phone Cord should always be towards the end
as indicated on
the name-plate.
READY
LED-will light up when the TELEPHONE INTERFACE II is
ready to communicate.
POWER LED-will light up when the AC Adapter is plugged into the
Power Jack on the end (and
is connected to asource of 120 Volts AC
power) and mode switch is not OFF.
Originate/OFF/ Answer Switch-Determines the mode of operation.
Set to 0for the Originate mode. Set to
OFF to tum the unit off
(POWER LED will be ofO. Set to Afor the Answer mode of operation.
Power
Connector-Connect the AC Adapter to this jack.
Full/TEST/Half Switch-Determines duplex function. Set to Ffor
full-duplex operation. Set to
TEST for an audio self-test mode. Set to H
for half-duplex operation.
DATA I/O Connector-This mates with the standard EIA DB-25
connector from an RS-232-C interface such
as Radio Shack's 26-1145.
4

INSTALLATION
1. Set O/OFFI ASwitch to OFF.
2. Plug AC Adapter into asource of 120 Volts, 60 Hz AC powet
Connect the other end to the Power connector on the end
of the
TELEPHONE INTERFACE II.
3. Connect the cable from the RS-232-C Interface to the DATA 1/0
connectot
4. Set F/TEST/H switch to the desired duplex mode (or Test mode if
desired).
S. Set O/OFF/A switch to Originate or Answer as desired. The
POWER LED will light up.
OPERATION
Originate Mode
1. Set O/OFFI Ato 0and F/TEST/H as required.
2. Establish contact with the remote terminal (dial number, assure a
good, noise-free phone connection, etc.).
3. Press the telephone handset firmly into the acoustic coupler cushions,
with the cord positioned
as labeled (PHONE CORD • ).
4. When the READY LED comes on, the TELEPHONE INTERFACE
II
is ready to handle data communications.
S. Proceed with data communications.

Answer Mode
1. Answer the telephone (call from remote terminal). Assure that the
phone connection is aclear, noise-free one. Obtain
or deliver
appropriate voice instructions.
2. Set
O/OFFI Ato Aand F/TEST/H as required.
Note: In Answer mode, you'll hear atone at all times, with or without
READY LED being lit.
3. Press the telephone handset firmly into the acoustic coupler cushions,
with the. cord positioned as labeled (PHONE CORD ~ ).
4. When READY LED comes on, proceed with normal data exchange.
To terminate acall, set O/OFFI Ato OFF and hang up the telephone.
Test Mode
The Test mode is designed to verify that the TELEPHONE INTERFACE
II is functioning correctly. It does this by switching the transmitter
channel frequencies to match the receiver frequencies. All data into the
modem is looped back into the Computer for verification.
It requires a
telephone handset to provide an isolated acoustic path between earpiece
(transmitter) and mouthpiece (receiver).
Originate
In this sequence, the Computer should be set up for full duplex
operation.
Set TELEPHONE INTERFACE II to Originate and use TEST
position of F/TEST/H switch. You will hear atone from the earpiece
cushion;
if no tone is present, the unit is defective or the setup is
incorrect.
Dial asingle digit
on the phone to silence the line; immediately place
the handset into the rubber cushions.
Note: Aquiet line is required for this test sequence. Some phone
company exchanges will not maintain aquiet line situation long enough
to complete the test; in such asituation, you must dial an extension
or
other number which can be controlled (cover the mouth-piece of this
second phone to prevent background noise pickup).
6

Wait for the READY LED to come on. lYpe amessage and the TEST
function will display the message on the Video screen; check display for
accuracy.
Answer
If modem passes the TEST in Originate mode, switch to the Answer
mode (with handset still on the TELEPHONE INTERFACE II).
When READY LED comes on, type amessage and it should
be
displayed on the Video screen.
Note:
If the READY LED comes on in both Answer and Originate
modes, but no message (or incorrect message, such as double characters)
appears on the Video screen, the RS-232-C
or cables or the Expansion
Interface may
be at fault. If the Computer can be put into an "echo"
mode by connecting pins 2and 3together at the modem end of the
RS-232-C cable and the me.ssage is correct, then the TELEPHONE
INTERFACE II is at fault.
7

Trouble Shooting
I( you have problems, the most likely cause is the phone line. Noise on the
line or aweak phone line signal can often result in lost or invalid data.
Try to
re-dial the call to insure that the connection is noise-free and there
is no
interference.
If communication still can not be established and the TELEPHONE
INTERFACE II checks out in the TEST mode, refer
to the chart below.
Symptom Problem/Solution
READY LED is off Is power
"on"?
Is handset properly positioned in
rubber cushions (cord toward RS-232-C
cable end)?
Are mode switches set properly?
1. When communicating with time-share
computer, modem must be in Originate
mode.
2. When communicating with another
TRS-80, mode selection must be agreed
upon before data transmission. (One
modem must be
in Answer mode and
other in Originate mode.)
3.
For data communication, duplex switch
must be in either Full
or Half position (not
TEST).
4.
Is modem at the other end compatible
with the TELEPHONE INTERFACE II?
(See specs.) Remote modem should be
either another TELEPHONE INTERFACE
II, aBell
103 or equivalent.
Communication can not
be established
with aBell 202 type.
Double Character Is system
in half-duplex mode?
Display
I( remote computer echoes all
characters, the TRS-80 system must
be in the Full-duplex mode.
I( communication system is half-
duplex (no echo), either RS-232-C
or TELEPHONE INTERFACE II (not
both) must be
in half-duplex.
8

Symptom Problem/Solution
Garbled Display Is telephone handset firmly seated in robber
cushions? Is baud rate correct? Both local
and remote computer systems must send data
at the same rate (300 baud or less). Is
received signal too weak
or noisy? Pick up
hand-set and listen for aclean tone
(If remote
modem is in answer mode).
If additional
tones, dialing pulses, static noise or voice
sounds are present, data may be garbled.
Re-place the call.
9

Data Interface
The TELEPHONE INTERFACE II provides an RS-232-C interface via a
standard 2S-pin female D-connector (labeled: DATA I/O). The table
below lists the signals used by the TELEPHONE INTERFACE II.
Outputs: Mark (Off): -8V
Space (On): +
lOY
Inputs: Mark (Off): -3 TO -2SV
Space (On): +3TO +2SV
Pin Connections
Function Signal Direction
2BA
3BB
1hlnsmit Data Input to modem
Receive Data Output to computer
SCB
6CC
7 AB
8CF
Clear
to Send
(On with
Carrier Detect)
Data Set Ready
(ON with
Carrier Detect)
Signal Ground
Carrier Detect
Output to computer
Output to computer
Output to computer
Output to computer
to