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.

0

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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

2

3

4

5

6

7

9

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

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 -

30

31

·1

31

32

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4

8

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19

21

22 ,

24

26

28

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10

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13

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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-

---

()

;o

.,

"'

....

~

.... ....

'""

--

'

0

I

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Jl

JL

,,,

Figure

3.

Data

Cabinet

11

\I

ill

r

1

:1_~

·I!,

1:

r

I.

I =

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

9

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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

'

I

,:

'j'.'

''I

''

11,

i!

I I

Ji

I,

)

I,•

'I

,,

'·

1,

I '

I

·''

-------------

·--

·--------·-------

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

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'

I'

, I

I

!

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i,

~

,,,

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ii

,'

-!

!1

I,

~I

l

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11

;jl,

.:

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~

ii

11•

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::!I:

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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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AT&T 202T User manual

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