AT&T 202T User manual
AT&T
Information
Systems
I
FCC
WARNING
STATEMENT
Federal
Communications Commission (FCC) Rules
require
that
you be notified of
the
following:
•
This
equipment
generates, uses,
and
can
radiate
radio frequency
energy
and
if
not
installed
and
used
in
accordance
with
the
instruction
manual,
may
cause
interference
to
radio
communications.
•
It
has
been
tested
and
found to comply
with
the
limits
for
Class A computing device
pursuant
to
Subpart
J of
Part
15 of
the
FCC Rules, which
are
designed to provide
reasonable protection
against
such
interference
when
operated
in
a commercial
environment.
•
Operation
of
this
equipment
in
a
residential
area
is likely to cause
interference
in
which
,case
the
user
at
their
own expense will be
required
to
take
whatever
measures
may
be
required
to
correct
the
interference.
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999-
102-
142IS
USER'S
MANUAL
202T
MODEM
Copyright
®1984
AT&T Technologies
All
Rights
Reserved
Printed
in U.S.A.
ISSUE
1,
MARCH
1984
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INTRODUCTION . . . .
How to Use This Manual
DESCRIPTION
Functional Description · •
Features
of
the
202T Modem
Physical Desc:i;iption
47B1
Data
Mounting
40B1
Data
Mounting
202T Modem Lights
202T Modem Switches
INSTALLATION PREPARATION
Power
Tools Required
Environmental Requirements
Cabling .
Cabinets
The 202T Modem ·Options
, INSTALLATION PROCEDURES
Installing
202T Modem Options
CONTENTS
4-Wire Modem
Terminated
by a 42A Connecting Block
4-Wire Modem
Terminated
by a 549A
Jack
..
'
4-Wire Modem on 4-Wire
Private
Line
With
the
829
Network Interface
Data
Only
........................
.
4-Wire Modem Connected to Locally Engineered
Private
Line Termination Without
Page
1
1
2
2
2
2
3
4
4
5
6
6
6
6
7
7
9
17
17
18
19
21
the
829
Network Interfaces . . . . . . . . . . . . . . . . . . . .
23
2-Wire Modem Connected to Locally Engineered
Private
Line .
Termination . . . . . . 24
Multiple Modem
Installation
•
26
TESTING PROCEDURES
Local Self-Test
Analog Loopback Test
Remote Test (4-Wire Operation)
- 1 -
29
29
29
29
Remote
Test
(2-Wire Operation)
SERVICE INFORMATION
Defective
Units
APPENDIX
Figure
1.
202T Modem
Front
View
Figure
2.
202T Modem
Rear
View
Figure
3.
Data
Cabinet
LIST OF
FIGURES
Figure
4.
Location of Option Switches
Figure
5.
4-Wire Modem
Terminated
by a 42A Connecting Block
Figure
6.
4-Wire Modem
Terminated
by a 549A
Jack
. . . .
Figure
7.
4-Wire Modem on 4-Wire Privat~ Line
With
the
829
Network Interface,
Data
Only . . . . . . . . . . . . . . . . . .
Figure
8.
4-Wire Modem Connected
to
Locally Engineered
Private
Line
Termination
. . . . . . . . . . . . . . . . .
Figure
9.
2-Wire Modem Connected to Locally Engineered
Private
Line
Termination
. . . . . . . . . . . . . . . . .
Figure
10.
Block
Diagram
of 30-Inch
Data
Cabinet Equipped
With
Eight
Modems
..................
.
LIST OF TABLES
TABLE
A.
202T Modem Options
TABLE
B.
Recommended Options for 2-Wire
Private
Line
and
4-Wire
Private
Line
With
Talk-Back Using
the
202T Series modem . . . .
'.
. . . .
TABLE
C.
Recommended Options for 4-Wire
Point-to-Point
and
Multipoint.Without
Talk-Back Using
the
202T Series Modem
TABLE
D.
DTE
Interface
TABLE E.
Private
Line
Interface
-ii -
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21
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24
26
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INTRODUCTION
This manual gives you
the
information needed to install and
test
the
202T
modem. Operating
procedures
are
limited to
the
use of
the
test
switches and lights. A brief physical and
functional description is provided and is intended for those who understand
data
communications in general.
How
to Use This
Manual
To
ma,k<:l
the best use of this•manual,
take
the
time to
read
it
through completely to become
familiar with
its
contents and organization. Then, for quick access to information needed to
answer most questions, you will only have to refer to
that
specific section.
To
answer
que13tfons
requiring more information
than
this
manual contains, consult your
Account Executive.
This manual is divi'ded into six sections.
•
Description
-This
section gives you a general description of
the
modem and briefly
describes
its
capabilities. Also included is a description of
the
lights, switches, and
optional units.
•
Installation
Preparation
-This
section tells you
the
environmental
considerations, power
and
wiring requirements, and how to identify and choose
the
proper options for your modem.
•
Installation
Procedures-This
section gives step-by-step instructions on how to
install
the
options
and
the
modem
in
a single or up to five modems in a multiple
arrangement.
•
Testing
Procedures-This
section allows you to verify the proper op~ration of
the
modem by telling you how to
do
various
test
procedures using
the
modem
test
switches
and
lights.
•
Service
In.formation-This
section tells you how to obtain service for your modem.
'
•
Appendix-The
Appendix includes supplemental information including tables
showing
the
Data
Terminal Equipment (J?TE)
and
private line pin assignments.
Page 1
I'
DESCRIPTION
This sectio.n provides a
brief
functional and physical description of
the
202T modem. The
functional description also provides
the
features.
available to
the
user. The physical
description will enable
the
user
to locate
the
various lights, switches, and options.
Functional Description
The 202T modem is a
data
communications device;
permitting
your
data
terminal
to send
and
receive
data
up to 1400 bits
per
second (bps)
without
reverse channel
and
up to 1200 bps
with
reverse channel over your basic
3002
private lines. The modem sending
data
at
speeds
between 1400 and 1800 bps, require C2-conditioned
3002
private
lines with
or
without
reverse
channel.
In
2-wire service,
the
modem can be equipped with a reverse channel circuit pack
for signaling speeds up to 5 bps in
the
opposite direction to
the
primary
channel. In 2-wire
service,
the
modem operates in
the
half-duplex mode (2-way nonsimultaneous).
In
4-wire
service,
the
modem operates in
the
full-dupl~x mode (2-way simultaneous). This operation is
achieved by frequency
shift
keying (FSK) modulation techniques.
Features of the
202T
Modem
The modem features include
the
following:
• Half-duplex (2-wire)
or
full-duplex (4-wire) operation
•
Data
rates
from 0 to 1800 bps.
1.
With
reverse channel, 0 to 1200 bps.
2.
Without
reverse channel, 0 to 1400 bps.
3.
With
or
without
reverse channel over C2-conditionea
3002
private lines, 0 to
1800 bps.
• Asynchronous, binary, and serial
data
operation.
•
FSK
modulation.
• Designed to be
terminated
with
the
829
Network Interface in
a:
single
or
multiple
arrangement,
549A Jack,
or
42A Connecting Block.
• Electronic
Industries
Association (EIA)
standard
RS-232-C Interface.
•
Test
switches
and
lights for performing self-tests and monitoring
the
status
of
the
modem.
• Reverse channel (optional)
that
can be ordered separately.
Physical Description
The 202T modem is contained on a
printed
circuit wiring board
and
can be installed in a
variety
of configurations. The modem
may
be mounted in
an
aluminum 47Bl (stand-alone)
data
mounting
with
removable plastic
front
and
rear
covers,
or
in a 40Bl (multiple)
data
mounting housed in a
data
cabinet.
Page 2
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4781 Data Mounting
The 47Bl
data
mounting
measures 5.8 inches wide, 10.8 inches long,
and
2.2
inches high. The
weight
with
the
modem installed
without
reverse channel is about 3.5 pounds.
It
weighs
about
4 pounds
with
reverse channel. The 47Bl
data
mounting
comes
with
a 6-foot power
cord
that
plugs into a
standard
117 Vac, 3-wire grounded
outlet
not
under
the
control of a
switch. The modem uses a
maximum
of 7
watts
of power. Figure 1 shows a 202T modem
installed
in
a 47Bl
data
mounting.
l'
'\....-
STATUS
LIGHTS
-
--1
'----
Figure
1. 202T Modem
Front
View
TEST
SWITCHES
Page 3
The 47Bl
has
cut-outs for two interface connectors and a power cord on
the
rear. One
connector provides
the
interface between
the
modem and your
Data
Terminal
Equipment
(DTE). The
other
connector provides
the
interface between
the
modem
and
the
private
line
network. Figure 2 shows
the
rear
view of a 202T modem installed
in
a 47Bl
data
mounting.
40B1
Data
Mounting
DTE
INTERFACE
(FEMALE)
/
POWER
SUPPLY
CORD/
Figure
2. .202T Modem
Rear
View
The 40Bl
data
mounting is installed on 23-inch framework within
·a
data
cabinet. The
data
mounting measures
23
inches wide (including mounting bracket); 13.5 inches long,
and
7
inches high. The weight of
the
data
mounting is
about
21
pounds
without
any
modems
installed. ·
The 40Bl
data
mounting includes a 4-foot power cord with a 3-wire male plug on one end
and
a 3-wire twist-lock female connector on
the
other
end. ·
Every
slot
in
the
data
mounting is wired, making
it
possible to install up to
16
modems
without
reverse channel and 8 modems
with
reverse channel.
202T
Modem
Lights .
The 202T modem
has
six
status
lights behind
the
front
cover.
Each
light, when on
illuminates a portion of
the
front
cover displaying a 2-letter graphic. The lights and
their
functions
are
described below:
•
ON-The
ON
light
is illuminated as long as power is available
at
the
modem, and
must
be lighted for
the
modem to function.
Page
4
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•
MR-(Modem
Ready): Illuminated when
the
data-set-ready lead is
high.
Modem
ready
on
means
the
modem is ready for
data
communications.
• RS-(Request-to-Send): Illuminated when
the
request-to-send lead is
high.
The
request-to-send indication is a signal to
the
modem from
the
terminal equipment to
transmit
data.
• CS-(Clear-to-Send): Illuminated when
the
clear-to-send lead is
high.
The clear-to-
send indication is a signal to
the
terminal
equipment from
the
modem to begin
transmission. ,
•
CO-(Carrier
On): Illuminated when
the
received-line-signal detector lead is high.
Carrier
On means a proper line signal is being received by
the
modem.
···
-
.-TM-(Test
Mode): Illuminated when
any
of
the
test
switches
are
pressed,
but
will
extinguish
if
an
error
is detected
in
the
local self-test mode.
Note:
~he
TM,
MR,
RS,
CS,
and
CO
lights
are
illuminated when
the
Remote Test (RT)
or
Local Self-Test (LT) switch is pressed, if
the
modem is being used for 2-wire
operation. If
the
modem is being used for 4-wire operation, only the
TM
light is
illuminated when
the
remote
test
(RT) switch is pressed; however, all lights
are
illuminated when.the Local Self-Test (LT) switch is pressed.
202T Modem Switches
The 202T modem has
three
switches on
the
front
panel. The Analog Loopback (AL)
test
and
Remote Test (RT) switches
are
push-to-operate, push-to-release,
and
are used for local and
remote
testing
of
the
modem. The Local Self-Test (LT) switch is nonlocking, and is used for
local
testing
of
the
modem.
For
normal
data
operation, all of these switches should be in
the
out
(released) position. When operated,
the
switches condition
the
modem
as
follows:
•
AL-(Analog
Loopback): This switch connects
the
output
of
the
modem
transmitter
to the
input
of
the
modem receiver. The line is disconnected from
the
modem,
and
the
modem-ready circuit is held OFF.
• LT--'-(Local Self-Test): This switch con,nects
the
transmitter
output
to
the
receiver
input
and
conditions
the
modem to operate
with
built-in word
generator
and word
comparator circuits. The line is disconnected from
the
modem, and
all
the
modem
output
circuits
at
the
DTE interface
are
held OFF.
•
RT-(Remote
Test): The functions performed by
the
RT switch depend on whether
the
modem is
arranged
for 2-wire or 4-wire operation.
In
both
2-
and 4-wire
operation,
the
output
circuits to
the
DTE interface
are
held OFF.
With 2-wire operation,
the
modem is conditioned similar to
the
local self-test mode except
the
modem is connected to
the
line. This allows
the
modem to be tested from a remote
location.
With
4-wire operation,
the
output
of
the
demodulator is connected to
the
input
of
the
modulator to loopback incoming signals from a remote location.
Page 5
INSTALLATION PREPARATION
This
sectioD;
provides
information
for
preparing
to ·
install
a 202T modem m a ·single
arrangement
or
up to
48
modems in a multiple
arrangement.
Power
Electrical power is supplied to single modem
installations
by
an
external
transformer
which
plugs into a 105- to 129-volt,
at
57- to 63-Hz nonswitched 3-wire
outlet
that
you
must
provide.
The
transformer
is protected
internally
against
overload. Multiple modeni
installations
(rack or cabinet)
are
powered by
an
ac power supply in
the
data
mounting
that
connects
to
the
nonswitched 3-wire
outlet
that
you provide. These power outlets should be
easily accessible
to
the
modem
and
should be served from
the
same
ac
distribution
panel
as
the
DTE.
The
power outlets should
not
share
power
with
other
electrical devices
that
may
cause noise. The power required per modem is
about
7
watts.
The power outlet(s) should
not
be
under
the
control of a switch.
Caution:
Your
power
outlet
should
have
a
plastic
cover.
However,
if
your
outlet
has
a
metal
cover
do
not'
remove
the
center
screw
to
.mount
the
transformer.
When
this
screw
is
removed
it
is
possible
for
the
metal
cover
to
fall
across
the
prongs
of
the
transformer.
Components
requiring
outlets include:
• The 202T modem.
• An
829
network interface.
• Your DTE.
Tools Required
A
standard
screwdriver, wire cutters,
and
wire
striper
are
requ\red
if
you use a 42A
Connecting Block
or
505A
Jack
/ 549A
Plug
private
line
network
interface. No special tools
are
required
if
you use
an
829
Network Interface. A
standard
screwdrive:r: is required when
you change
the
modem options. Cords
are
installed, in general, by conriecting cables
and
cords to
the
modem connectors. Refer to
the
illustration
for installation·
instructions
for
that
station
arrangement.
Environmental Requirements
The
modem should be located on a table, shelf,
or
in
a
data
cabinet
within
50
feet of
its
DTE.
The
modem will
operate
over
an
ambient
temperature
range
of
40
degrees
Fahrenheit
with
a
relative humidity of
20
to'
95
percent
at
70
degrees
Fahrenheit
and
20
to
40
percent
at
120
degrees
Fahrenheit.
Note:
These environmental conditions apply only
if
condensation does
not
accumulate
on
the
internal
modem components.
Page
6
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Cabling
You
must
provide a DTE
interface
cord
not
to
exceed
50
feet in length equipped
with
a Cinch
or Cannon DB-19604-432 plug equipped
with
a DB-51226-1 hood (or equivalent). This cord is
connected to
the
25-pin female connector
at
the
rear
of
the
modem.
The
private
line
must
meet
the
transmission
requirements
of
the
3002 channel. As
part
of
the
private
line channel service,
an
829
network interface, or 549A Jack,
or
42A Connecting
Block is provided.
The
202T modem
may
be located
as
far
as
lQ00
feet from
its
network
interface. ·
To minimize inductive interference to
data
signals on
the
private
(data) line channel,
the
channel should
not
be located in
the
same
run
as
the
cable between
the
modem
and
the
DTE,
or-lines
connected to ·teletypewriter services.
If
this
condition
cannot
be ·met,
it
will be
necessary to
run
the
channel wiring in shielded cable between
the
modem
and
the
cable
distribution
terminal
or
building entrance. The shield should be grounded
at
the
distribution
terminal
only.
Cabinets
The
cabinets used
for
multiple modem
arrangements
are
designated 17-inch
data
cabinet
(one 40Bl
data
mounting), 30-inch
data
cabinet (two 40Bl mountings), and 72-inch
data
cabinet
(three
or
four 40Bl
data
mountings).
Each
cabinet is made of aluminum
with
a clear
anodized finish
and
a
perforated
rear
panel of black anodized aluminum. The
front
panel is
tinted
plastic, so
the
modem lights can be seen from outside
the
cabinet. A
data
cabinet is
shown in Figure
3.
The outside dimensions
and
weight
of
the
data
cabinets
are
as
follows.
• 17-inch
data
cabinet
-
17
inches high,
24
inches wide,
and
19
inches deep.
It
weighs
23
pounds.
• 30-inch
data
cabinet -
30
inches high,
24
inches wide,
and
19
inches deep.
It
weighs
34
pounds.
• 72-inch
data
cabinet'"
72
inches high,
2~.5
inches wide,
and
26
inches deep.
It
weighs
230
pounds.
Page
7
·--~-
----------------------~
lo
ol
o
ON
o
ON
o
ON
oON o
ON
o
ON
o
MR
oMR oMR
oMR
o
MR
oMR
o
RS
oRS oRS o
RS
o
RS
,oRS
O
cs
oCS O
cs
oCS O
cs
O
cs
0
co
oCO oCO oCO 0
co
oCO
o
TM
o
TM
o
TM
o
TM
o
TM
o
TM
D D D D D D
------
D D D D D D
r r r r r r
I- I-
- - --
r r r r r r
.... ....
....
....
....
::!
I- I-
---
()
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.,
.,
.,
.,
"'
....
~
~
~
.... ....
'""
--
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,,,
Figure
3.
Data
Cabinet
11
\I
ill
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1
:1_~
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1:
r
I.
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Page 8
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The 202T Modem Options
The 202T modem is provided with numerous options
that
should be selected prior to placing
the
modem in service. These options
must
be compatible with your DTE. Check your DTE
manual
for options
that
may be required. Figure 4 shows
the
location of
the
option switches.
Removal of
the
reverse channel circuit pack is described in
the
INSTALLATION
PROCEDURES section under Installing 202T Modem Options.
The option switches or
strap
is used to select
the
various options. The options for
the
202T
modem
are
listed in Table
A.
The options marked '.'factory-provided"
are
the
most
commonly used. The recommended options for 2-wire private line and 4-wire private line
with
talk-back using
the.
202T series modems
are
listed in ·Table
B.
The. recommended
options for 4~wire point-to-point
and
multipoint without talk-back using the 202T series
modems
are
listed in Table
C.
OPTIONS
SWITCHES
1
THRU
5
CLOSED
{ROCKER
DOWN
ON
SIDE
ADJACENT
TO
THE
NUMBERS)
OPTION
SWITCH
S4
OPTION
SWITCHES
6
THRU
10
OPEN
{ROCKER
DOWN
ON
SIDE
OPPOSITE
THE
NUMBERS)
202T
MODEM
(MODULATOR-
DEMODULATOR)
LOCAL
COPY
Figure
4.
Location of Option Switches
REVERSE
CHANNEL
Page
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-
--•-----~-----------
----------------
TABLE
A
202T
MODEM
OPTIONS
FEATURE
OPTION
DESCRIPTION
SWITCH
SETTING.
53
SWITCH
CONTACT
SETTING
ON
TRANSMITTER-RECEIVER
1 2 3 4 5 6 7 8 9 0
4-Wire
Operation
ZK*
0 --0 -X X X X X
ZD
w/o
Reverse
Channel
X --X -X 0 0 0 0
2-Wire
Operation
zct
With
Reverse
Channel
X --X -0 0 0 0 0
Compromise
Delay
zv
Minimum
-X - - ------
Equalization zu•
Maximum
-0 - - -- - ---
Compromise
Amplitude
zx
Minimum
- - - - X -----
Equalization
zw•
Maximum
-- - - 0 ---- -
zz
C2
- - X -------
Channel
Condition zy• Basic 0
-------- -
'
~2
SWITCH
CONTACT
SETTING
ON
,!TRANSMITTER-RECEIVER
' "
1 2 3 4 5 6 7 8 9 ().
4-Wire
Operation
ZK*
X ---------
Local
Copy
on
Primary
ZA
In X -- - ----- -
Channel
in 2-Wire
ZBt
Out
0 -- - ----- -
SOFT
SQUELCH
TURNOFF
z 0 - 0 -X - - -0 X 0 - -
·-
Y*
8
ms
0 -X ---0 0 0 --
X
24
ms
0 -X - - -0 0 X - -
Soft Turnoff
and
w 0 9
ms
-0 - - -0 X 0 - -
Squelch
Intervals
V 0
156
ms
-0 - - -X X 0 --
T 8
ms
9
ms
-0 - - -
o.
0 0 - -
s 8
ms
156
ms
-0 ---X 0 0 - -
R
24
ms
156
ms
-0 ---X 0 x --
Fast Carrier
Q*
In - - 0 -- - -
~
_, -
Detection N
Out
X
- - -- - - - - -
M*
8
ms
- -
,-
0 --- - -0
..
K
30
ms
'·
- - -
O·
~~
-
·-
--X
Clear-to-Send
Interval
J
60
ms
-
...,
-X - - - --0
G
180
ms
-- - X - - ---X
Page 10
PROVIDE
One
Per
Modem
One
Per
Modem
()
' )
One
Per
Modem
One
Per
Modem
One
Per
Modem
0
One
Per
Modem
. I
One
Per
Modem
One
Per
Modem
4
0
I(
h
~
FEATURE
OPTION
External Control of
B*
CC
(Data Set
Ready)
A
F*
Clamp
E
TABLE
A (Contd)
202T
MODEM
OPTIONS
DESCRIPTION
In --
Out
--
In --
Out
--
SWITCH
SETTING
-- - -- - 0 -
-- - - - - X -
- - 0 -- - --
- - X -- - --
S4'.~WITCH
CONTACT
SETTING
ON
··-·
--···
--
Carrier Detector
ZL
In
Reset
ZM*
Out
ZN
in
Continuous Carrier
zo•
Out
State
of
CC
YB
On
(Data Set
Ready)
During
Analog
YA*
Off
Loopback
Local
Copy
on
Reverse
Channel
ZE
In
ZFt
Out
Grounding
Option Signal
Ground
ZG*
-Connected to
(Modem)
Frame
Ground
Signal
Ground
ZH
Not
Connected
Frame
Ground
Signal
Ground
ZI*
Connected to
Grounding
Option
Frame
Ground
(Data
Mounting)
Signal
Ground
ZJ
Not
Connected
Frame
Ground
X
Rocker
down
on
side adjacent to
numbers.
0
Rocker
up
on
side adjacent to
numbers.
-
Rocker
may
be
in
either
position.
* Factory furnished.
TRANSMITTER-RECEIVER
1 2 3
-X -
-0 -
X - -
0 - -
--X
--0
STRAPPING
ON
REVERSE
CHANNEL
CP
Install
E21-E22
Install
E21-E23
SCREW
SWITCH
Sl
SETTING
ON
INTERFACE
CIRCUIT
Sl Closed
to Sl
Open
,
STRAPPING
ON
4OB1
DATA
MOUNTING
Wire
Strap
if
Power
Supply In
Wire
Strap
if
Power
to
Supply
Out
t Factory furnished instead of 4-wire option
when
reverse channel
CP
is
installed.
-
PROVIDE
One
Per
Modem
One
Per
Modem
One
Per
Modem
One
Per
Modem
One
Per
Modem
One
Per
Modem
One
Per
Modem
Page
11
'
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,:
'j'.'
''I
''
11,
i!
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I,•
'I
,,
'·
1,
I '
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·''
-------------
·--
·--------·-------
TABLE
B
RECOMMENDED OPTIONS
FOR
2-WIRE PRIVATE
LINE
AND
4-WJRE
PRIVATE
LINE
WITH TALK-BACK USING
THE
202T-SERIES
MODEM
FAR
END
202C;
2020,
OPTION
NEAR
END
OR
202R (NOTE)
Received
Data
Squelch 156 ms
IN
Clear-to-Send Delay 180 ms
200
ms
Fast
Carrier
Detection OUT (Normal)
(23
ms)
40
ms
Soft
Carrier
Turnoff
24
ms
IN
Received
Data
Clamp
IN IN
Alternate
Voice Optional Optional
Switched Network Backup Optional Optional
Reverse Channel Optional in 2-Wire
Private
Line Optional in 2-Wire
Private
Line*
Carrier
Detector Reset
Not
Used
Not
Offered
Local Copy Optional in 2-Wire
Private
Line Always Provided for 2-Wire Modem
Continuous
Carrier
OUT-Carrier
Under
Coptrol of
Carrier
Controlled by Request-to-
Request-to-Send
Sendt
Note:
If
far-end
modem is a 202T-series
the
recommended options
are
the
same
as
those
for
the
near
end.
*
Not
offered with
the
202R modem.
t
Not
offered with
the
202C
or
D modem.
=
Page 12
1w
I,
J',j
()
0
(()
()
0
TABLE
C
RECOMMENDED OPTIONS
FOR
4-WIRE POINT-TO-POINT AND
MULTIPOINT WITHOUT TALK-BACK USING
THE
202T-SERIES
MODEM
OPTION
RECOMMENDATION
Clear-to-Send Delay 8 ms
if
remote
modem is a 202T-series
with
fast
mode
carrier
detection.
,
,7
••
30
ms
if
remote
modem is a 202T-series
with
normal
mode
carrier
detec-
tion
or
a 202R, 202D5,
or
D6 with 40,ms
carrier
detector
timing
.
.-
60
ms
if
remote
modem is a 202C, 202D3, 202D4,
or
a 202R, 202D5, or
•-
..
-..
..,
....._ 202D6 with
the
40-ms
carrier
detector timing.
Fast
Carrier
Detection
IN
(fast
mode) if
remote
modem is a 202T-series
with
8-ms clear-to-send
delay.
OUT (normal mode)
if
remote
modem is optioned for
30c
60- 180-
or
200-ms
! clear-to-send delay.
Soft
Carrier
Turnoff
24
ms
if
remote
modem is a
202C,
202D3, D4,
D5,
D6, 202R, or 202T with
normal
mode
fast
carrier
detection.*
8
ms
if
remote
modem is a 202T-series
with
fast
carrier
detection option.
Quick
turnoff
if remote modem uses
carrier
detector
reset
option.
Received
Data
Clamp IN
Carrier
Detector
Reset
IN-at
master
station
of
broadcast
polling
or
bridge~
multipoint
system
when
remote
modem use
the
quick
carrier
turnoff
and
master
station
is
able to
implement
this
circuit.
OUT-all
other
times.
Continuous
Carrier
IN-for
point-to-point applications and for modem
as
master
station
_of
split
bridge
multipoint
systems.
OUT-may
be used for abpve applications and should be used for modem
at
the
remote
station
of
split
bridge
multipoint
system.
Alternate
Voice Optional
(with
829
netw<frl<
interface).
Switched Network Backup Optional (with
829
network
interface).
* The 202T-series modem
must
be optioned for
the
8-ms
or
quick
turnoff
interval when the
interval
between consecutive
turnoffs
of
the
request
to s.end
circuit
is less
than
165 ms.
The options
and
their
functions
are
described next:
•
2-Wire
Operation:
This
option is used when 2-wire facilities
are
selected
and
half-
duplex service is satisfactory. The 2-wire option
can
be selected
with
reverse channel
(ZC) or
without
reverse channel (ZD).
If
option
ZC
is selected,
the
modem
must
be
equipped
with
a reverse channel
circuit
pack,
and
option ZE or ZF
must
be selected.
If
option ZD is selected,
the
reverse
channel
circuit pack
must
be physically removed
from
the
modem.
•
4-Wire
Operation:
This
optiO'Il
is used when 4-wire point-to-point or
multipoint
facilities
are
selected.
The
4-wire option used
with
4-wire facilities provides duplex
capability.
Page 13
. I
Ir
ij
I I
'
I'
, I
I
!
:'I
i,
~
,,,
I
ii
,'
-!
!1
I,
~I
l
!1
11
;jl,
.:
;f
~
ii
11•
I
::!I:
I
',
::,!
l
•
Compromise
Delay
Equalization:
Option
ZV
(minimum compromise· delay
equalization) provides reduced envelope delay
distortion
compensation
to
eliminate
an
overequalization condition on channels
with
low envelope delay distortion. Option
ZU ·(-maximum compromise delay equalization) provides
the
same
delay equalizer
characteristics
provided on modems
without
the
delay equalizer options.
For
data
bit
rates
above 1200 bps,
it
is necessary to
perform
a
data
distortion
test
to
determine
the
proper delay equalizer option setting.
Note:
If
the
necessary
equipment
to
perform
the
compromise delay
and
compromise amplitude equalization t~sts is
not
available,
the
optimum
setting
where minimum
errors
occur should be used.
•
Compromise
Amplitude
Equalization:
Option
ZX
(minimum
compromise
amplitude equalization) effectively removes compromise amplitude equalization,
and
is required on lines
with
high-end delay distortion
near
the
upper
limit
and
amplitude distortion
near
the
lower
limit
of
the
3002 specification.
Without
this
option,
this
combination of distortions
may
cause
parity
errors
at
1200 bps. Option
ZW
(maximum compromise amplit~de equalization) provides
the
same
amplitude
equalization
as
the
202T modem.
•
Channel
Condition: These options, modify
the
demodulator
for
operation over C2-
conditioned lines (ZZ)
or
basic lines (ZY).
• -
Local
Copy
on
Primary
Channel
in
2-Wire:
With
this
option installed,
the
receiver continuously
monitors
the
transmitted
line signal while
in
the
data
mode
and
provides a local copy on
the
received
data
circuit.
•
Soft
Turnoff
and
Squelch
Intervals:
Page 14
1.
When a
data
terminal
turns
request-to-send
off
at
the
end of a message,
transients
occur which
may
cause ~purious signals
to
be received
at
a
distant
station.
With
the
soft
carrier
turnoff
option,
the
modem
transmits
out-of-band
carrier
(900
Hz) for a period of
either
24
or
8
ms
after
request-
to-send is
turned
off. This option should be used in conjunction
with
the
received
data
clamp option
and
results
in a
steady
mark
on
the
received
data
circuit of
the
remote modem. The 8-ms option should be used when
the
remote
modem
has
the
fast
received line signal
detector
option.
The
24-ms
option should be used when
the
remote
modem is 202D, 202R,
or
202T series
with
the
normal
received line signal detector option. However,
the
24-ms
option
must
not
be used when
the
interval
between consecutive
turnoffs
of
request-to-send circuits is less
than
165 ms.
Neither
the
8- ·nor 24-ms option
should be used
at
the
remote
stations
of a
multipoint
system when
intermessage
intervals
are
less
than
10 ms.
For
this
case,
the
0-ms (quick
turnoff)
option should be used
(at
the
remote
stations)
in conjunction
with
the
received
data
clamp
and
the
carder
detector'
reset
options
(at
the
master
station).
With
the
0-ms (quick tur,noff) option,
carrier
will be
turned
off in less
than
1 ins
after
the
request-to-send circuit is
turned
off.
Note:
In
2-wire applications for t~rminals which immediately
turn
on
request-to-send
as
soon
as
the
I received line signal detector goes
off,
the
8-ms
soft
turnoff
option
ii
incompatible
with
the
8'-ms clear-
to-send
interval
option,
and
the
24-ms
soft
turnoff
option is
incompatible
with
the
8-
and
30-ms clear-to-send
intervaloptions.
2.
In
half-duplex operation on 2-wire facilities, when a
station
that
has
been
transmitting
has
its
request-to-send circuit
turned
off,
the
telephone line
may
reflect signals (echoes) back to
that
station
for a period up
to
the
()
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