in

in

of

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made

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A.

1873.

was

Board tuning

and

known, in

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early

met

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in

substi­

university

His

been

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the

which be

order

shop

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Watson

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to an

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paired

not

Speech

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he by

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Boston

Bell,

Brantford,

1873.

of

one

his

investigate

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not

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Boston,

same

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in

to

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in

place

Bell

to

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was the

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made

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Graham

requested

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of

Jr.,

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the

Bell

telephone

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1

Bell

he basis.

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him

experiments

was models

COMMUNICATIONS

anatomy

England,

been

instruments.

young

the

as

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instruments duties

training

led

inventors.

office

procedure,

that

OF

1.1

University, with

continued

Watson,

and

telegraph Graham

had Bell

intentions, the the

led

from

Alexander

considered

Early

Williams,

assisted

CHAPTER is

his

speak. the

first

Bell,

this abandoning

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known,

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who

with

TELEPHONE

to

home-study

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interest

Boston electrical

Bell

also

in

HISTORY a

Graham

delivered

Bell's

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Bell

father

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THE

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harmonic After

bench Morse

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OF

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with

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of

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his

with

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1867,

1870, In

Charles

organs.

mostly

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services

less on

the

over most

who

In

experiments in

As speech, for

develop Bell's

unsatisfactory; Some

work;

but

late

Physiology

he rather

work

and to

INVENTION

of

job to England

a

teaching

Education

accordance

out

founded

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graphy tuting

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music, Ontario. conduct migrated occupation tuned-reed instruments forks New ties Vocal in the 1874, hours. simultaneously.

proved

was

viously. after Bell's went Watson,

was

by by

of of

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the the

of of

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for for

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and and

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to to

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son son

who who

money. money.

a a

a a

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basic basic

by by

per per ••• •••

is is

battery battery

types types

needed needed

it it

a a

are are

smoked smoked

patents patents

a a

an an

had had

and and

deaf deaf

interrupted interrupted

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with with

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Watson, Watson,

Visible Visible

Bell, Bell,

written written

.•• .••

on on

Koenig, Koenig,

burdensome. burdensome.

needed needed

Hubbard Hubbard

by by

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needed needed

tuned-reed tuned-reed

forward, forward,

a a

any any

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instruments instruments

over over

any any

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to to

1874 1874

make make

early early

by by

money money

intensity intensity

according according

larger larger

his his

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Bell Bell

his his

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improvements improvements

much much

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The The

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number number

telegraph telegraph

telegraph telegraph

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to to

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Bell, Bell,

COMMUNICATIONS COMMUNICATIONS

who who

electromagnet electromagnet

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function, function,

speech." speech."

improving improving

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oscillographs oscillographs

embodied embodied

Accordingly, Accordingly,

Sanders, Sanders,

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outlined outlined

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to to

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OF OF

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density density

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historical historical

human human

the the

I I

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soon soon

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1.2 1.2

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Scott, Scott,

1875. 1875.

offer offer

studying studying

Thomas Thomas

and and

1875 1875

harmonic harmonic

to to

Hubbard, Hubbard,

also also

clockspring clockspring

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sound sound

means means

mechanism mechanism

modified modified

an an

furnish furnish

HISTORY HISTORY

current current

in in

the the

experimenting experimenting

27, 27,

"Manometric "Manometric and and

experiments experiments

G. G.

mechanical mechanical

contact contact

intended intended

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Leon Leon

through through

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electric electric

instruments, instruments,

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electricity electricity

instruction instruction

screw." screw."

steel steel

magnet magnet

this this

and and

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of of

obtained obtained

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get get

assistance assistance

BRIEF BRIEF

through through

of of

about about

early early

Oscillograms Oscillograms

deaf, deaf,

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air air

even even

Laboratories' Laboratories'

possible possible

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arrangements arrangements

of of

were were

transmitter, transmitter,

operation operation

battery battery tuned-reed tuned-reed

transmitter transmitter

three three

from from

the the

can can

a a

also also

actuated actuated

concurrently concurrently

February February

with with

1 1 - Gardiner Gardiner

were were

the the

1874, 1874,

be be

the the

follows: follows: I I

work work

the the

the the

ordinary ordinary

connected connected adjustable adjustable

contact contact

time, time,

similar similar

The The

The The

of of

made made

as as

cost cost

all all

on on

telegraph telegraph

of of

of of

each, each,

CH. CH.

as as

as as

current current

sound, sound,

to to

passing passing

Bell Bell

•.• •.•

Bell's Bell's

technique, technique,

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Financial Financial

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informal informal

the the

plates plates

and and

might might

constructed constructed

it it

Telephone Telephone

first first

Phonautograph Phonautograph

fall fall

benefited benefited

the the

Watson, Watson,

fied fied the the were were

Speech Speech

principle principle

Bell Bell

glass glass harmonic harmonic

phonautograph. phonautograph.

the the

acoustically acoustically

Morey. Morey.

found found

agreement agreement

Bell, Bell, Fortunately, Fortunately, These These

problems problems

Sanders, Sanders,

had had which which CH. 1 - BRIEF HISTORY OF COMMUNICATIONS

second that corresponded to the pitch of the reed. This intermittent current, passing through the telegraph wire to the distant receiver, set the reed of that receiver into vibration sympathetically if it was of the same pitch as the transmitter reed. If the two reeds were not of like pitch, the receiver would not respond to the current." "3. If six transmitters with their reeds tuned to six different pitches were all sending at once, their intermittent currents through the magnets of six distant receivers with reeds tuned to the same pitches, each receiver would, theoretically, select from the mix-up its own set of vibrations, and ignore all the rest."

A. EARLYEXPERIMENTS »ell and Watson continued to experiment with models of instruments made by Watson as described above. In one room they set up: 1. Three circuit breaking transmitters, tuned to different pitches, each provided with a telegraph key to connect it with a battery and the line wire as desired, and 2. A set of three tuned-reed receivers having the same pitches as the transmitting instruments. In the other room, designated as the receiving station, another set of three tuned-reed receivers, identical with the three receivers in the sending room, were connected to the far end of the line. Working with this experimental arrangement on June 2, 1875, Bell, at the receiving station at the far end of the line, made the critically controlling discovery, reported by Watson as follows: "I had charge of the transmitters as usual, setting them squealing one after the other, while Bell was retuning the receiver springs one by one, pressing them against his ear ..•. One of the transmitter springs I was attend­ ing to stopped vibrating and I plucked it to start it again. It didn't start and I kept on plucking it, when suddenly I heard a shout from Bell in the next room, and then out he came with a rush, demanding: 'What did you do then? Don't change anything! Let me see?' I showed him. It was very simple." 1.3 CH. 1 - BRIEF HISTORYOF COMMUNICATIONS

The contact point of the transmitter which Watson was trying to start evidently was screwed too hard against the spring, so that when he snapped the spring the circuit had remained unbro~en.Continuing with Watson's report: " •.• that strip of magnetized steel, by its vibration over the pole of its magnet, was generating that marvelous conception of Bell's -- a current of electricity that varied in intensity precisely as the air was varying in density within hearing distance of that spring. That undulatory current had passed through the conn~cting wire to the distant receiver which, for­ tunately, was a mechanism that could trans­ form that current back into an extremely faint echo of the sound of the vibrating spring that had generated it, but what was· still more fortunate, the right man had that mechanism at his ear during that - fleeting moment, and instantly recognized the transcendent importance of that·f~int sound thus electrically transmitted. The shout I heard and his excited rush into my room were the result of that reco.gni­ tion. The speaking telephone was born at that moment." After trying many variations of their first success­ ful transmission, with and without a battery in the circuit, Bell instructed Watson late on June 2, 1875, to build a new instrument, the one which has since come to be kn.own as Bell's first telephone. A stretched parchment diaphragm. which had been contemplated by Bell. while working with the human ear specimen in the summer of 1874, was now added to the previous type of coil and reed receiver assembly, with certain modifications. This first telephone, a "Gallows Frame" Magneto (Figure 1-1) was tried out, as a transmitter on the night of June 3, 1875, the receiver being one of the tuned-reed harmonic telegraph instruments used_ previously. Later on, two of the new telephones were used as trans­ mitter and receiver. Whereas the harmonic telegraph tuned­ reed instruments, when used in pairs, were found capable of transmitting and receiving the fundamental and harmonics of a vibrating spring, the new telephone was capable of trans­ mitting and receiving speech sounds which were more complex, but it still was not good enough to transmit intelligible speech.

1.4

At At

a a

and and

come come

7, 7,

This This

by by

fully fully

heard heard 1876, 1876,

in in

in in

of of

the the

it it

he he

trans­

had had

he he years years

1876, 1876,

his his

the the

he he

the the

the the

induc­

to to

of of

connec­

three­

was was

an an

completed completed

him him

variable­

in in

crude crude in in

instruments instruments

device device

and and

March March

in in

1-2) 1-2)

then then

when when

be be

later later

conductor conductor

Watson, Watson,

as as

A A by by

March, March,

that that

feasibility feasibility

liquid liquid

one one

the the

capable capable obtained obtained

on on

to to

frequency. frequency.

objective. objective.

application, application,

wire wire

Office Office

summoned summoned

in in

desired desired

of of

Watson Watson

methods, methods,

was was

speech speech

1-3) 1-3)

further further

these these

early early

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used used

for for

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original original

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Patent Patent

patent patent

reported reported

to to

and and resistance resistance

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application, application,

the the

to to

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at at

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assigned assigned

Bell Bell

pursued pursued

method method

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the the

a a

an an

having having

considered considered

this this

1876, 1876,

the the

22. 22.

COMMUNICATIONS COMMUNICATIONS

early early

1875, 1875,

a a

provided provided

patents patents

Messrs. Messrs.

line line

for for

for for

This This

issued issued

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in in

electrical electrical

was was

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OF OF

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built built

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1.5 1.5

excitedly excitedly

call call

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of of

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1174,465 1174,465

moment" moment"

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and and

in in

and and

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transmitter transmitter

then then

up up

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be be

last last

additional additional

battery. battery.

HISTORY HISTORY

which which

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Watson Watson

a a

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Bell Bell

essentially essentially

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latter latter

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1174,465 1174,465

BRIEF BRIEF

claim claim Watson Watson

current" current"

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type, type,

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of of

1876, 1876,

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Telegraphy, Telegraphy,

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night night

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Watson Watson

the the

you!" you!"

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development development

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APPLICATIONS APPLICATIONS

telegraph telegraph

resistance resistance

old; old; 14, 14,

group group

Patent Patent

the the

the the

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to to

consisting consisting

want want

CH. CH.

supplied supplied

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request, request,

On On

with with

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to to

connected, connected,

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prepared prepared

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association. association.

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"parent "parent

PATENT PATENT

years years

January January

stretched-diaphragm-type stretched-diaphragm-type

(acidulated (acidulated

tion tion

of of

established. established.

spilled spilled every every

to to

here, here,

stationed stationed 29 29

closed closed

including including

device device

harmonic harmonic

Watson Watson original original

cornerstone cornerstone Improvement Improvement

been been

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decided decided resistance resistance

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tion. tion.

undulating undulating February February

1876 1876

on on specification specification

a a

Bell Bell mitter, mitter,

B. B.

Sanders, Sanders,

man man current current Bell Bell

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HISTORY HISTORY

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COMMUNICATIONS COMMUNICATIONS

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34 34

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1.9 1.9

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(Figure (Figure

the the

Francis Francis

Bell Bell

were were

became became

(Figure (Figure

a a Western Western

a a

party's party's

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transmitter transmitter

dis­

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formal formal

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Bell Bell

held held

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microphone microphone

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through through

telephone telephone

you you

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patent patent

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and and

butterstamp butterstamp

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device device

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transmitter transmitter

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dairy dairy

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COMMUNICATIONS COMMUNICATIONS

a a

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method, method,

important important

Bostonian Bostonian

draw draw

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OF OF

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voice voice

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Berliner, Berliner,

transmitter transmitter

Western Western

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ordinary ordinary

historic historic

inventor inventor

over over

contact contact

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1.10 1.10 that that

as as most most

contact contact

Alexander Alexander operated, operated,

customers customers

Bell Bell

young young

1-3) 1-3)

of of

a a

day. day.

to to

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patent patent

with with a a

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resembled resembled

transmitted transmitted

that that

you you

HISTORY HISTORY

the the

Emile Emile

Blake Blake

bit bit

coil, coil,

(your) (your)

installation installation

phone phone

central central

decided decided

the the

come. come.

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within within

receiver, receiver,

the the

as as

thought thought

it it

year, year,

in in

" "

of of

the the

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was was

transmitter transmitter

to to

of of

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transmitter transmitter

attach attach

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dial. dial.

of of

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transmitting transmitting was was

time, time,

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chassis chassis

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BRIEF BRIEF

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.••• .•••

telephone telephone

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phone. phone.

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age age

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years years

induction induction

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handle, handle,

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phone phone

rotary rotary

established established

States States

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for for

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patent, patent,

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Made Made

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pay pay

11 11

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invented invented

its its

receiver receiver

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instrument, instrument,

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receiver receiver

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to to

Bell Bell

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1-3). 1-3).

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Blake Blake

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cranked cranked

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hence hence thumping thumping

ing ing bined bined

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piece piece

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the the

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jacks jacks

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sub­

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where­

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set set

was was

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evolution evolution

deskstand­

transmission transmission

The The

parties, parties,

1-5). 1-5).

many many

flexible flexible

the the

It It

conversing. conversing.

1937, 1937,

products, products,

materials, materials,

the the

to to

produced produced

family family

many many

The The

"500" "500"

TrimlineR TrimlineR

made made

additional additional

instrument instrument

the the

the the

business. business.

desk desk

three three

two two

which which

number number

of of

industry-wide industry-wide

telephone. telephone. the the

in in

In In

appear appear

saw saw

obtain obtain

in in

into into

those those

to to

manually manually

have have

the the

(Figure (Figure

to to

that that

type type

comprising comprising

avalanche avalanche

Then Then

put put

lines, lines,

over over

only only

have have

devices devices

of of

design. design.

basic basic

magnetic magnetic

so so

As As

supply supply

drawings, drawings,

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play play

cord cord

connect connect

connected connected

quickly. quickly.

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buttons buttons

used used

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Telephone Telephone

side side

disconnect. disconnect.

a a

hand-held hand-held

COMMUNICATIONS COMMUNICATIONS

not not

may may

began began

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the the

telephone telephone

day-to-day day-to-day

set. set.

"300" "300"

present-day present-day Toucft-ToneR Toucft-ToneR

reach reach

To To

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by by

came came

OF OF

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subscriber subscriber

1.11 1.11

"settled" "settled"

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side side

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the the

service service range range

almost-everything-resistant, almost-everything-resistant,

a a

and and

come come

of of

plastics plastics

ends ends

ends. ends.

Picturephone Picturephone in in

color color

a a

possible possible

are are

1919 1919

"French "French

to to

thereafter thereafter

to to

switchboard switchboard

as as

also also be, be,

HISTORY HISTORY

attractive attractive

subscribers. subscribers.

ringing ringing

were were

off off

the the

this this

operator operator

the the

phone phone

have have

produce produce

lines; lines;

the the

both both

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first first

These These

With With

contained contained

placed placed

connect connect

one one

and and

but but

makes makes

150 150

for for

to to

carrying carrying

soon soon

need need

became became

operator operator

on on

out out

first first

BRIEF BRIEF

The The

vintage vintage

and and

by by

the the

to to

that that

taken taken

be be

the the

in in

accouterments accouterments 1-3. 1-3.

if if

1878 1878

nonfading, nonfading,

set set

the the

transmitter transmitter

and and

the the

transmitter transmitter

1 1 - 1919 1919

One One

tap tap plugged plugged

SWITCHBOARD SWITCHBOARD

additions additions

sets. sets.

voice voice

hand, hand,

serve serve

positions positions

1927 1927

are are

receivers, receivers,

1-4) 1-4)

new new

began began

was was

in in

plugs plugs

colors. colors.

with with

materials materials

line. line.

could could

service service

to to

recent recent

and, and,

of of 1950, 1950,

use use

wall wall

in in

Figure Figure

and and

CH. CH.

telephones. telephones.

the the

and and

a a

of of

In In

Of Of

FIRST FIRST

switches switches combines combines

other other

Between Between

human human Later Later

While While

bell bell

New New

could could

switchboards switchboards in in

with with

in in

into into

as as

System System

(Figure (Figure

operator operator

telephone. telephone.

long-life, long-life, receiver, receiver,

the the

the the

telephone telephone

the the

THE THE

the the

capacities. capacities.

associated associated

rotary rotary

positions positions

switchboard switchboard customers customers

scriber's scriber's Indications Indications

signaling signaling

the the

of of

the the

in in

early early set set

the the

former former

followed followed

C. C.

on on

which which

designs designs receiver receiver

wires wires

came came of of

shown shown

usefulness usefulness

processes processes

used used

variety variety colored colored

Bell Bell

both both with-dial with-dial

COMMUNICATIONS COMMUNICATIONS

1-4 1-4

OF OF

1.12 1.12

Figure Figure

HISTORY HISTORY

BRIEF BRIEF

1 1 - CH. CH. CH. 1 - BRIEF HISTORY OF COMMUNICATIONS

Figure 1-5

The Bell System's new Model II PICTUREPHONE set can be used to transmit drawings or charts by setting the camera focus at one foot. In the photograph, the "self-view" option is being used to position the graph while it is being transmitted.

1.13

of of

the the

his his

this this

net­

day­

Though Though

to to

city, city, the the

system system

feet feet

of of

sub­

was was

tele­

connect connect

simple simple

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the the

too too

made made

to to

to to

Vail, Vail,

trolleys, trolleys,

sub­

the the

a a

the the

early early

Western Western

possibili­

90 90

to to

one-way one-way

efforts efforts

infancy. infancy.

during during

NETWORK NETWORK

he he

tide tide

N. N.

Telegraph Telegraph the the

telephone telephone

21 21

alarm alarm

in in

as as

Connecticut, Connecticut,

none none

switchboards. switchboards.

for for

the the

city city

the the

its its

over. over.

Ontario. Ontario.

dimension dimension

switchboard switchboard

and and

nationwide nationwide

the the

answer answer

together together

the the

slow: slow: issued. issued.

that that

and and

1877, 1877,

of of

connections connections

of of

Boston, Boston,

to to

a a

greater greater

high high

in in

commercial commercial

using using

of of

remembered remembered

new new

The The

distribution distribution

was was

in in

was was

Haven, Haven,

burglar burglar

signal signal

telephony, telephony,

patents, patents,

of of

as as

Theodore Theodore tied tied

back back

too, too,

May, May,

world world

successful successful

three three

a a

has has

lines lines

be be

a a

Paris, Paris,

multiple multiple

much much

a a in in

design design

by by

8 8

in in

New New

the the

441 441

of of

linking linking

COMMUNICATIONS COMMUNICATIONS

interconnect interconnect

the the

to to

Responsible Responsible

idea idea

Telephone Telephone

hold hold

growth growth

power power

note note for for

COMMUNICATIONS COMMUNICATIONS

up up

poles poles

which which

in in

must must

strictly strictly

concern, concern,

(permanent (permanent the the

of of

added added

OF OF

to to

wires. wires.

very very

and and

Holmes, Holmes,

attributed attributed

nation nation

to to

to to

used used

The The

it it

directory directory

set set

in in

1.14 1.14

born. born.

"This "This

T. T.

to to

be be

300 300

and, and,

rapid rapid

how how

commutation commutation

was was

how how

first first

was was

inventors inventors

developing developing

multiple multiple

statement statement

E. E.

holder holder

was was

American American

electric electric

EXCHANGE EXCHANGE

Brantford Brantford

miles, miles,

Bell Bell

can can

a a

and and

a a

HISTORY HISTORY

the the

Bell, Bell,

in in

proclaimed proclaimed

Scribner. Scribner.

Trunking Trunking

yet." yet."

sky; sky;

exchanges exchanges

one, one,

era, era,

The The

of of

8 8

previously previously

NATIONWIDE NATIONWIDE

two, two,

and and

the the

networks. networks.

positions) positions)

in in

nation nation

of of

established established

A A

E. E.

progress progress

of of

of of

and, and,

interconnecting interconnecting

from from

was was

remarked, remarked,

the the

interesting interesting

classified classified

manufacturing manufacturing

1876, 1876,

but but

of of

BRIEF BRIEF

and and

OF OF

prolific prolific

and and

light light

technology technology

a a

apparatus apparatus

was was

the the

he he

came came

1880's, 1880's,

time time

is is

office office

added. added.

know know

night. night.

TELEPHONE TELEPHONE

switch switch was was

1 1 -

crossarms crossarms

1878, 1878,

provided provided

event event

increased, increased, of of

number number

ships; ships; It It

first first

gas gas

and and

Charles Charles

most most

lines lines

we we

the the

problems: problems:

the the

at at

the the

circuit circuit

August August

switchboards switchboards

switching switching

state state

was was

30 30

when when

block block

contribution contribution

communications communications

CH. CH.

the the

ORIGINS ORIGINS

nonadjacent nonadjacent

In In

and and the the

the the

At At

In In

FIRST FIRST In In

the the

to to

Much Much

President President

problem problem two two

blackening blackening

exchange exchange

wires wires

than than

of of

and and

banks banks

distance distance

of of

THE THE

was was

effect effect

January, January,

THE THE

ties ties

first first

Company, Company,

first first

state state

increasing increasing

work work carrying carrying

scriber's scriber's

trains trains

posed posed

wires wires It It

primitive. primitive.

in in communications communications in in

period period

time, time,

scribers. scribers.

four four

phone phone

telephone telephone

the the

plug plug

strong, strong, 1.2 1.2

A. A.

telephone telephone greatest greatest

one one

telephone telephone

Electric's Electric's "Jack-Knife" "Jack-Knife"

subscribers subscribers

between between positions positions

as as

of of

of of

- a

plus plus

to to

wires wires

inven­

open open

of of

wires wires

long long

the the

were were

be be

thick thick

intervals intervals

extended extended

was was

of of

from from

careful careful

triumph triumph

channels channels

the the

"Phantom "Phantom

service service

much much

thousands thousands

the the

of of

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crosstalk crosstalk

of of

power power

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as as

heavy heavy

over over

simulta­

multichannel multichannel

authorized authorized

needed. needed.

desert desert

to to

transporta­

via via

Boston Boston

and and

line line

on on

to to

There There

could could

been been

in in

single single

pair pair

beginning beginning

to to

into into

the the

electro­

and and

wasn't wasn't

-

benefits benefits

of of

the the

led led

of of

were were

time, time,

It It

"circuit"), "circuit"),

These These

had had The The

an an the the

conversations conversations

from from one one

Carty's Carty's

wires wires

led led

almost almost

specified specified

came came

out out

put put

a a

telephone telephone

reached reached

the the

adoption adoption

which, which,

-

strung strung

and and

theory theory

of of

wires wires

J. J.

its its

at at

eliminating eliminating

loaded. loaded.

line line

lines lines

line line

theory theory

from from be be

quadrupling quadrupling

was was

8, 8,

the the

discovered, discovered,

three three

turn, turn,

instead instead that that

Pupin, Pupin,

COMMUNICATIONS COMMUNICATIONS

marked marked

Washington, Washington,

for for

were were

or or

John John

wires wires

unsurpassed. unsurpassed.

called called

inductance inductance

Denver. Denver.

cables. cables.

thus thus

discovery discovery

problem problem balance balance

-

two-way two-way

in in plains plains

I. I.

coils coils

line line

for for

number number

OF OF

(No. (No.

could could

circuit circuit

1883, 1883,

first first

of of

of of

and and

is is

to to

in in

of of

to to

1.15 1.15

and, and,

phantoming. phantoming.

telephone telephone

wires wires

the the

two two

9, 9,

the the

This This distance distance

events events

Campbell Campbell

telephone telephone

the the

his his

This This

by by that that

1886 1886

second second

really really

inductively inductively

tripling tripling

wires wires

which, which, ground, ground,

pairs pairs

a a

miles miles

York-Chicago York-Chicago

wires wires

Michael Michael

A. A.

May May

HISTORY HISTORY

long long

adding adding

transmitting transmitting

in in

University, University,

other other

channel channel

"loading" "loading"

the the

These These

across across

the the

project project

of of

giving giving

the the

was was

two two

possible possible

On On

construction construction

lines. lines.

New New

responsible responsible

reduced reduced

of of

rods, rods,

the the

to to

telephone telephone

1880, 1880,

copper copper

filter filter

extended extended

from from

over over

Philadelphia Philadelphia

BRIEF BRIEF

obtained obtained

and and

distance distance

George George

and and developed developed

was was

and and

the the

2, 2,

over over

of of

System. System.

thousand thousand

pairs pairs

also also

to to

like like

it it

LOADING LOADING

1884. 1884.

Professor Professor Columbia Columbia

wires, wires,

authorized. authorized.

1 1 -

locating locating the the

through through

wave wave

Albany. Albany.

method method

telephone telephone

large large

answer answer

also also

pairs. pairs.

CIRCUIT CIRCUIT

loading loading of of

1911 1911

1889, 1889,

of of

application application

a a

June June

methods, methods,

was was

stretching stretching

over over

of of

27, 27,

to to

poles, poles,

by by

Lines Lines

pairs pairs

York York

CH. CH.

was was

circuit circuit the the

venturesome venturesome

Campbell Campbell

He He

with with

In In

In In

pencil), pencil),

The The

On On

-more -more

on on

Transmission Transmission

with with

of of

return return

other other

accumulated accumulated

whereby whereby

New New

and and

pairs pairs

interference interference

Carty Carty

Long Long

York York

York York

two-way two-way

engineering engineering

additional additional

poles poles

INDUCTIVE INDUCTIVE

PHANTOM PHANTOM

March March

third third

lead lead

(a (a

two two

of of

of of

telephony. telephony.

an an

inductive inductive

realized realized

tion tion

big big

a a

a a

along along

tion tion

wires wires distance distance

the the

into into doubling doubling

built built

neously neously

the the

C. C.

before, before, physicist physicist on on

lines. lines. that that simultaneously simultaneously

Circiut," Circiut,"

wires wires from from

B. B.

with with

balanced balanced New New

practical practical

balancing balancing Mr. Mr. New New

-

a a

in in

too too

a a

been been

of of

be be

was was

they they

to to

dropped dropped

by by

who who

minute. minute.

lab­

to to

mid-'14 mid-'14

that that

in in

of of

this this

somehow somehow

from· from·

Bell, Bell,

that that

had had

a a

Francisco, Francisco,

initiated initiated

were were

but but

has has

In In

from from made made

Omaha, Omaha,

electrical electrical

could could

became became

point point

that that

scientists scientists

use use

arc arc

of of

grown grown

for for

speech speech

Francisco Francisco

that that

San San

attic attic

official official

coast coast

was was

imperfect imperfect

would would

was was

the the

call call

Graham Graham

importance, importance,

transcontinen­

they they

they they

people people

to to

has has

San San

route route

perfected perfected

- it it

engineers engineers

a a

since since

the the

critical, critical,

too too

knew knew

telephone telephone

year, year,

from from

telephone telephone

System System

amplifiers amplifiers

amplifier amplifier

in in

first first

Chicago, Chicago,

repeaters repeaters

Nevada. Nevada.

for for

mercury mercury

transcontinental transcontinental

up up

in in

Paris. Paris.

the the

effort effort

magnified magnified

or or

Bell Bell

fraction fraction

The The

capacity capacity

way way

was was

practical practical

line line

of of

where where

being being

possibility, possibility,

they they

before before

hoped hoped

to to

same same

the the

held held

on on

extreme extreme

Bell Bell

radio radio telephone telephone

tube tube

scale scale

weak weak

COMMUNICATIONS COMMUNICATIONS

the the

Alexander Alexander

for for

the the

long long

continent continent

Watson Watson

of of

need need

was was

already already

kind kind

but but

small small

single single

the the

by by

the the

device device

this this

level level

left. left.

setting setting

OF OF

a a

were were

too too

of of

route route

a a

a a

began began

a a

points. points.

conversations conversations

the the

In In

assistant assistant

first first

placed placed

large large

the the

by by

1.16 1.16

1915, 1915,

Pittsburgh, Pittsburgh,

Winnemucca, Winnemucca,

Vacuum Vacuum

amplifiers, amplifiers,

some some

currents currents

were were

to to

for for

time time

Atlantic Atlantic

development development tube, tube,

this this

cumbersome, cumbersome,

to to

end end

come come

Thomas Thomas

to to

were were

Coast, Coast,

From From

the the

of of his his

circuits, circuits,

an~ an~

when when

promising promising

up up

nothing nothing

HISTORY HISTORY

the the

to to

York, York,

and and

and and

the the

slender slender

time time

hour hour

across across

has has

there there

distant distant

the the

voice voice

first first

City. City.

tube tube

before. before.

been been

breakthrough breakthrough

an an

was was

New New

City City

where where

demonstrated demonstrated

them them

to to

and and

three three

1915. 1915. was was

The The

call call

1906, 1906,

Recognized Recognized

and and

the the

BRIEF BRIEF

the the

conversations conversations

January January

construction construction

really really

primitive primitive

crude crude

developing developing

mechanical mechanical

more more

in in

across across

had had

Lake Lake

Basically, Basically,

in in

in in

-

heretofore heretofore

to to

half half

coast-to-coast coast-to-coast

in in

years years

Lake Lake

Philadelphia, Philadelphia,

research research

vacuum vacuum

or or

that that

to to

be be

long long

on on

There There

1 1 -

for for

too too

build build

a a

telephone telephone

and and

Boston Boston

Virginia, Virginia,

who who

-

this, this,

Denver Denver

trial trial

1913, 1913,

at at

Salt Salt

to to

TUBE TUBE

was was

on on

call call

the the

CH. CH.

in in

office office

And, And,

Salt Salt

which which

on on

that that

sorts sorts and and

forty forty

The The

to to

In In

It It

ultimately ultimately

But But

furnishing furnishing

respond respond

depend depend

about about

thousands. thousands.

an an

technological technological

system. system.

either either

first first

Watson Watson

projection. projection.

Deforest. Deforest.

"audion" "audion"

Hawaii, Hawaii,

a a adapt adapt

VACUUM VACUUM

line, line,

from from

simultaneous simultaneous

to to many many

historic historic

the the

transmitted transmitted

Arlington, Arlington,

from from transcontinental transcontinental

oratory oratory

nearly nearly

the the

coast. coast.

installed installed Denver, Denver,

to to Denver Denver

as as

communications. communications. concentrated concentrated

tal tal

the the

Lee Lee signals signals

long long response, response,

D. D.

amplifiers amplifiers

several several

feeble, feeble,

working working

were were

projected projected

exhaustion. exhaustion. extend extend

planned planned would would might might

a a

on on

to to

fast, fast,

of of

12 12

an an

the the

the the

in in

long long

A A

tele­

a a

are are

have have

marked marked

led led

art art

ampli­

develop­

ridding ridding

pipes pipes

in in

their their

of of

as as

and and

program program

rapidly. rapidly.

calls calls

ahead ahead

cable cable

Bend, Bend,

day day

of of

following following COMMUNITY COMMUNITY

in in

the the

of of

Using Using

to to

long-haul long-haul

the the

tremendously. tremendously.

the the

crossbar crossbar

that that

effort. effort.

as as

One One

York York

in in

to to

grew grew

Known Known

needs needs

The The

OFFICE OFFICE

Telephone Telephone

hollow hollow

356A 356A

stored stored

television, television,

pondered pondered

South South

veritably veritably

moving moving

switches switches

prior prior

amplifiers amplifiers

Laboratory Laboratory

New New

led led

The The

panel, panel,

problem problem

subscriber. subscriber.

the the

and and

applications applications AND AND

answer. answer.

nonloaded nonloaded

employed employed

had had

Bell Bell

improved improved

completing completing

had had

was was

a a

(ESS). (ESS).

through through

in in

installation installation

network network

the the

CENTRAL CENTRAL

equations equations

more more

the the

COMMUNICATIONS COMMUNICATIONS

too too

of of

follow. follow.

financial financial

the the

that that

and and

using using

and and

System. System.

was was

overcome. overcome.

has has

Ohio Ohio

3SSA, 3SSA,

systems systems

interested interested

revolutionize revolutionize

accumulates accumulates

between between

it it

OF OF

the the

and and

by by

distances. distances.

for for

transmitted transmitted

chance. chance.

and and

DIAL DIAL

Telephone Telephone

who who

that that

terms terms

industry industry

too, too,

Relay Relay

System System

1.17 1.17

1936 1936

signals signals

by by

being being

were were

multiplex multiplex

350A, 350A,

these these

long long

recorded recorded

step-by-step step-by-step

more more

which which

in in

telephone telephone

dial dial

concepts concepts

channels, channels,

operating operating

Bell Bell

Toledo, Toledo,

in in

discovery discovery

of of

Southworth, Southworth,

LOCAL LOCAL

work, work,

a a

-

of of

in in

HISTORY HISTORY

a a

envisioned envisioned

he he

- operator operator

a a

and and

of of

Radio Radio

AND AND

when when

possible possible

the the

intelligence intelligence

over over

completely completely

to to

C. C.

new new

chapters chapters

happen happen

engineer, engineer,

principle, principle,

think think

and and

an an

to to

felt felt

Switching Switching

BRIEF BRIEF

engineers engineers

between between

page, page,

made made

way way

to to

the the

of of

technological technological

not not

system system

Black, Black,

broad-band broad-band

transmission transmission

problem problem

wires, wires,

incapable incapable

1920's, 1920's,

SYSTEMS SYSTEMS

distortion, distortion,

George George

in in

1 1 -

communications communications

his his

hundreds hundreds

S. S.

aid aid

for for started, started,

lengthen, lengthen,

of of

FEEDBACK FEEDBACK

did did

Microwave Microwave

impact impact 1938, 1938,

network network

of of

research research

commercially commercially

blank blank

the the

Feedback" Feedback"

on on

began began

descriptions descriptions

switching, switching,

other other

same same

CH. CH.

destined destined

centralized centralized

STEP-BY-STEP STEP-BY-STEP

the the

in in

the the

SYSTEMS SYSTEMS

carrier carrier

with with

this this In In

In In

1 1

Later, Later,

Once Once

Electronic Electronic

amplification amplification

seemed seemed

areas areas -

lines lines

and and

used used

Harold Harold

its its

their their

growing growing

of of

very very

transmission transmission

of of

dielectric dielectric

brief brief

EQUIPMENT EQUIPMENT

SWITCHING SWITCHING quality quality

the the

DIAL DIAL

NO. NO.

NEGATIVE NEGATIVE

connecting connecting

Indiana. Indiana.

are are

fast fast 1927, 1927,

radar radar

and and 1.3 1.3

of of this this

fiers fiers

and and Laboratory Laboratory

Engineers Engineers

signal signal

accidental accidental

A. A. without without

presentation presentation systems systems

Philadelphia.and Philadelphia.and

added, added,

channel channel

E. E.

"Negative "Negative The The

solution solution

amplifiers amplifiers

pairs pairs

All All

ment ment scientist scientist

major major

phone phone

with with made made

or or

10 10

to to

to to or or

that that

and and

as as

by by

the the

of of

a a

for for

the the

into into

of of

office, office,

are are

in in

level level

next next

pulses. pulses.

cross­

sends sends

100 100

approxi­

addi­ the the

by by

in­

used used

being being

a a

busy busy

first first

large large

office, office,

line. line.

trunk trunk

digit digit

the the

service. service.

early early

Keith Keith

in in

to to

the the

a a

The The

basis basis

manner manner

be be

each each

by by

operates operates

series series

dial dial

array array

(automatic (automatic

cases, cases,

in in

from from

placed placed

of of

Indiana Indiana

through through

the the

in in

a a

1889 1889 E. E.

as as

to to

connection connection

a a

still still

offices offices

Today, Today,

at at

switches switches

an an

the the by by

not not

first first

in in

A. A.

use use

-

vacant vacant

was was up up

now now

efficient efficient

is is

were were

most most

switch switch type type

line. line.

places places

indicated indicated

the the

such such

through through

served served

switch, switch,

digits digits

a a

over over

by by

subscriber, subscriber,

office office

Forte, Forte,

the the

for for

in in

in in

could could

the the

anywhere anywhere

the the

and and

formed formed

patented patented

Waverly Waverly

subscriber's subscriber's

more more

La La

for for

two two

path path

switch switch

the the repeated repeated

units units

level level stacks stacks

move move

COMMUNICATIONS COMMUNICATIONS

being being

called called

activated activated

Exchange. Exchange.

in in

Strowger, Strowger, Company, Company,

the the

and and

is is

busy busy upon upon

implies, implies,

progressively progressively

OF OF

that that

equipment equipment

been been

where, where,

equipment equipment

the the

dialing dialing

the the

Step-by-Step Step-by-Step

system system

connector connector

final final the the

hunts hunts

shelves shelves

developed developed

B. B.

by by

rotates rotates

rings rings

called called

is is

1.18 1.18

developed developed

office office

still still

to to

switch switch

talking talking

had had

on on

this this

the the

Step-by-Step Step-by-Step

the the

Upon Upon

usually usually

areas areas

steps steps

the the

accommodate accommodate

switch switch

up up

was was

line. line.

line line

are are

level level

process process

unveiled unveiled

the the

Electric Electric

Almon Almon

HISTORY HISTORY

dial dial

digit digit

of of

Mulberry Mulberry

as as

each each

Telephone Telephone

serving serving

Depending Depending

semicircular semicircular

system. system.

switching switching

System, System,

may may

of of

was was

with with first first

the the

established established

of of

systems systems

systems. systems.

the the

steps steps

that that

contacts. contacts.

step-by-Step step-by-Step

in in

This This

mounted mounted

superseded superseded

lines lines

dialed dialed

last last

devices devices

BRIEF BRIEF

step-by-step step-by-step

system system

Although Although called called

panel panel

if if

connection, connection,

is is

known known

the the

at at

of of

at at stepping stepping

dialing dialing

switches. switches.

a a

are are

SYSTEM SYSTEM

the the

all all

name name

Automatic Automatic

1 1 -

systems systems

been been

office. office.

Automatic Automatic

multioffice multioffice the the

feasible feasible

Strowger Strowger

Jersey. Jersey.

digit digit

back back

call call

and and

brushes brushes

telephone telephone

undertaker, undertaker,

first first

1914 1914 of of panel panel

connectors connectors

1892 1892

sets sets

The The

on on

exchange) exchange)

such such

selector selector

the the

and and

the the

switching switching

arranged arranged

CH. CH.

has has

switch, switch,

DIAL DIAL

associated associated

rotary rotary

the the

electronic electronic

in in

New New

selector. selector.

In In

making making

10 10

a a

the the

subscribers. subscribers.

44% 44%

last last

tone tone

The The

The The

the the

of of

As As

establishment establishment

of of

City City

a a

it it

mechanical mechanical

switches switches

to to

of of

pulses pulses

of of

but but

and and

last last

Strowger Strowger

of of

contact contact

PANEL PANEL

the the

the the

busy busy

telephone telephone

fully fully

step-by-step step-by-step

service service

step-by-step step-by-step

bar bar

the the

Pewark, Pewark, telephone telephone

condition condition 10,000 10,000

advantageously. advantageously.

selector. selector.

to to indicated indicated

used, used, metropolitan metropolitan

terminal terminal

one one dial dial

tion tion

a a letter, letter,

series series

mately mately

another another B. B.

rows rows

The The

terminals terminals

the the a a

in in

others others

electromechanical electromechanical

commercailly commercailly

vented vented

1879 1879

These These

Kansas Kansas Automatic Automatic much much

the the

the the

The The

going going

and and

the the

to to

use use

oper­

di­

of of

this this

call call

of of

of of

a a

the the

been been

flexi­

control control

record record

it it

The The

move, move,

contact contact

it it

operator operator

as as sub­

with with

connec­

for for

and and

and and

the the

any any

path path

dialing dialing

systems systems

has has

motion, motion,

equipment equipment

close close

of of

switching switching

horizontal horizontal

system, system,

with with

banks. banks.

"marker" "marker"

where where vertical vertical

the the

completing completing

than than

groups groups

the the

of of immediately immediately

time, time,

direct direct office. office.

acts acts

to to a a

control. control.

rather, rather,

greater greater

idle idle

set set

in in

arrangement arrangement

unison unison

the the

the the

switches switches

no no

out out

consisting consisting

on on

and and

before before

transmit transmit

an an

When When

operated. operated.

in in

permits permits for for

controls controls

subscriber, subscriber,

but but

which which provide provide

of of

point, point,

control control first first

to to

is is developed developed

rather rather

Panel Panel

mechanical mechanical

movements movements

up up

multiple multiple

move move

employing employing

functions, functions,

direct direct

principal principal

member member

to to and and

a a

mechanical mechanical

drop drop

the the

and and

conjunction conjunction

the the

in in

Step-by-Step Step-by-Step

COMMUNICATIONS COMMUNICATIONS

speaking, speaking, was was

move move

seized seized

set set

trunking trunking

dial, dial,

This This

which which

the the

the the

there there

their their

allows allows

selector selector

in in

system, system,

"marked" "marked"

particular particular

common common magnet magnet

digits, digits,

OF OF

motors motors

seized. seized.

for for and and

from from

not not

equipment, equipment,

are are

etc., etc.,

is is

a a

device device

of of

rows rows

relation relation

A A

is is

diverging diverging

system, system,

through through

groups groups the the

the the

installations. installations.

a a

vertical vertical

the the

Panel, Panel,

selectors selectors

do do

This This

1.19 1.19

this this

found, found,

switching switching

magnetically magnetically

sender sender

necessary necessary

above, above,

use use

necessary, necessary,

as as

Panel Panel

a a

control control

generally generally

is is

in in

step step

the the

Calls Calls

next next

cause cause

is is

new new

member, member,

setting. setting.

call call extensive extensive

HISTORY HISTORY

common common

like like

switch switch

trunk trunk

SYSTEM SYSTEM as as

direct direct

dialing dialing

electric electric

which which

actually actually

in in

areas. areas.

each each

to to

the the

circuits circuits

a a

the the

it it

and and

subscriber's subscriber's

vertical vertical

the the

long long

for for

Crossbar Crossbar

it it

and and

system, system,

no no

noted noted

various various

by by

the the

each each

call call

briefly, briefly,

various various

the the

with with

will will

up up

are are

connectors, connectors,

operation. operation.

in in

1 1

DIAL DIAL

circuit. circuit.

over over

selectors selectors

BRIEF BRIEF

to to

as as

a a

with with

the the

proper proper

As As

logic logic

the the

flat flat

in in

is, is,

the the

dial dial

vertical vertical

have have

direction direction

Crossbar Crossbar

up up

the the

1 1 -

No. No.

sender sender

by by

panel panel

moved moved

repeated. repeated.

in in

which which

a a

Crossbar, Crossbar,

the the

members, members,

change change

efficient efficient

it it

paths paths

in in

complex complex

selectors selectors

1 1

registered registered

member, member,

receive receive

setting setting

is is

closed closed

of of

the the

set set

to to

The The

the the

the the

and and

are are

Therefore, Therefore,

CH. CH.

which which

markers, markers,

CROSSBAR CROSSBAR

panel panel

it, it,

utilized utilized

selector selector

metropolitan metropolitan

completed, completed,

associated associated progress progress

and and

is is

in in

possible possible

dials, dials,

more more

under under

remains remains

In In

proper proper

To To

1 1

In In

to to No. No.

Terminals, Terminals, more more

is is

extensive extensive

will will

is is

to to

is is

them them the the

a a

vertical vertical

hunting hunting

arranged arranged

call, call,

various various

hold hold

the the

remain remain

large large

called called

NO. NO.

selections selections

intervening intervening

tion tion

in in

senders, senders,

to to

operation operation

used used

springs springs

in in

operation operation

replaced replaced reduced. reduced.

basis, basis,

for for

and and

horizontal horizontal

element element

member member

over over

the the

than than

it, it,

using using

is is

C. C.

ates ates

of of

rect rect the the

trunks trunks

which which

bility, bility,

dialing dialing

control control electromagnets. electromagnets.

scriber scriber

dialing. dialing.

are are

selectors selectors which which

as as

in in

as as

areas areas

with­

11. 11.

local local

all all

13, 13,

a a

10-

for for

in in

use use with with

areas. areas.

1 1

with with

Message Message

the the

in in

is is

equipped, equipped,

advan­

as as

Distance Distance

Message Message

Automatic Automatic

the the

were were

serve serve

plan plan

amount amount

with with

to to

for for

with with

No. No.

so so

calls calls

to to

Crossbar Crossbar ANI ANI

for for

switching switching

can can

many many

office office

Office Office

the the

operate operate

Febr.uary Febr.uary

identify identify

the the

offices offices

not not

Direct Direct 2 2

permitted permitted

primary primary

provision provision

as as

and and

toll toll

Tandem Tandem

Automatic Automatic conversation conversation

to to

and and

(CAMA). (CAMA).

Identification Identification

on on

to to

to to

along along

dialing: dialing:

Automatic Automatic

operators operators

7-digit 7-digit

or or

for for

operates operates

center center

designed designed

local local

subscribers subscribers

numbering numbering

the the of of

The The

essential essential

common-control common-control

the the

type type

of of

reduces reduces

It It

a a

Others, Others,

toll toll

4 4

CAMA, CAMA,

Crossbar Crossbar

are are

and and

toll toll

this, this,

offices, offices,

Number Number

COMMUNICATIONS COMMUNICATIONS

is is

systems systems

information. information.

service service

Presi~ent Presi~ent

1 1

other other

party party

Crossbar Crossbar

senders senders

maintenance. maintenance.

with with

designed designed

number number

system system

call. call.

period period

This This

or or

customers, customers,

No. No.

OF OF

arranged arranged

to to

a a

Accounting Accounting

features features

two two

information information

using using

No. No.

20 20 Panel Panel

billing billing

centralized centralized

or or

lines. lines.

into into

this this

or or

less less Panel Panel

the the

been been

Before Before

of of

1. 1.

customer customer

Office Office

Step-by-Step Step-by-Step

or or

through through and and

system, system,

arranged. arranged.

operator. operator.

for for

call. call.

tandem tandem

this this

cut cut

and and

Automatic Automatic

over over

equipped equipped

and and

up up

conversion conversion

2000 2000

has has

switching switching

auxiliary auxiliary

HISTORY HISTORY

capacity capacity

and and

switching switching readily readily

and and

dialing dialing

CAMA. CAMA.

an an

Message Message

subscriber subscriber

record record

one one

Tandem Tandem

during during

translation translation

routing routing

It It

and and

offices, offices,

of of was was

are are

has has

(AMA) (AMA)

following following

a a

be be

pass pass

of of

than than

toll toll

operators operators

SYSTEM SYSTEM

type) type)

calls calls

up up

pulse pulse

Crossbar Crossbar

billing. billing.

another another

billing billing

System, System,

BRIEF BRIEF

in in

digit digit

Crossbar Crossbar

Panel Panel

setting setting

the the Conversion Conversion

5 5

can can

by by

feature, feature,

and and

similarly similarly

local local

and and

1 1

local local

York, York,

5 5

operator operator

for for

more more

10-digit 10-digit

distance distance

tied tied

1 1 -

telephone telephone

identify identify

Crossbar Crossbar

manually manually

the the

offices offices

Automatic Automatic

with with

(CAMA). (CAMA).

(AMA) (AMA)

No. No.

addition addition

Crossbar Crossbar

Code Code

Six-digit Six-digit

10-11 10-11 of of

Alternate Alternate

Marker Marker

New New

No. No.

routing routing

were were

digits digits

(non-AMA (non-AMA

No. No.

to to

to to

CROSSBAR CROSSBAR

CH. CH.

(DDD), (DDD),

Accounting Accounting

the the

number number

assistance assistance

with with

5. 5.

3. 3.

2. 2.

4. 4.

1. 1.

4 4

tandem tandem

5 5

toll toll

The The

Another Another

automatic automatic

The The

Some Some

provides provides

having having Crossbar, Crossbar,

enabled enabled

that that

direct direct

AMA AMA

machine machine

5 5

as as

first first

1 1

the the

hastens hastens

proceed proceed

NO. NO.

equipment equipment

combination combination

local, local,

expansion expansion

few few

a a

office. office.

and/or and/or

Dialing Dialing

Accounting Accounting

No. No.

1938. 1938. (ANI) (ANI)

areas areas

D. D.

Message Message

local local

CAMA CAMA

required required Brooklyn, Brooklyn,

calling calling

through through

No. No.

designed designed

The The

offices offices

digit digit

Centralized Centralized Crossbar Crossbar

out out tages tages

obtain obtain

alternate alternate

of of

and and Accounting Accounting and and CH. 1 - BRIEF HISTORY OF COMMUNICATIONS

The first No. 5 Crossbar Office went into service on July 11, 1948 at Media, Pennsylvania. 1.4 SWITCHING SYSTEMS - TOLL DIAL CENTRALOFFICE EQUIPMENT

A. TOLL APPLICATION Crossbar equipment can be used for switching toll traffic as well as local traffic. In the toll switching application, toll lines or trunks are switched to other toll lines or trunks, whereas in local switching, sub­ scribers' lines are switched to other subscribers' lines or trunks. Long distance operators and, in many areas sub­ scribers, can complete calls directly to subscribers in other distant areas on a dialing basis. For example, an outward toll operator in New York can dial a subscriber's number in any other city which has appropriate switching arrangements. No intermediate or end operator is required. With Direct Distance Dialing (DDD), no operator is needed at the originating end on certain types of calls. The general toll switching plan divides the United States and part of Canada into many numbering plan areas. Switching systems employing No. 4 Crossbar, Crossbar Tandem, No. 5 Crossbar and, in some cases, Step-by-Step Intertoll are provided at strategic points in each area. B. NO. 4A/4M TOLL SWITCHING SYSTEM This is a Crossbar Common Control Switching Point (CSP) system that provides 4-wire paths for establishing connections electromechanically on a nation-wide basis, between intertoll trunks, or between intertoll and toll connecting trunks. Operating on a destination route basis, it is capable of routing a call over a preferred route or any one of as many as six predetermined alternate routes automatically without operator assistance. The 4A System and its predecessor the 4M have the same features and operating capabilities. The No. 4 System uses multi­ frequency (MF) pulsing, that considerably shortens the time required for transmitting pulses controlling the switching equipment. Features essential to the operation of the No. 4, and to Direct Distance Dialing (DDD) are: 1. Crossbar switches, arranged on incoming and out­ going link frames, together with the necessary trunks and toll terminal equipment, care for the switching path.

1.21

of of

are are

any any

first first

and and

local local

small small

to to services. services.

Crossbar Crossbar

office office

senders, senders,

to to

Dialing Dialing switching switching

otherwise otherwise

which which

punch punch

and and

Required Required

1 1

the the

Major Major

the the

system system

switching switching

of of

switching switching

and and

is is Originally Originally

card card

as as

of of

completion completion

Switching. Switching.

No. No.

up up

pulsing pulsing

for for

Tandem Tandem

combining combining

volumes volumes

for for

Customer Customer

inpulsing inpulsing

and and

switching switching

the the

following following

succession succession

sets sets

Digits Digits

connecting connecting

by by

routing routing

of of

switching switching

translators translators

feasible. feasible.

equipment equipment

the the

Area Area

groups. groups.

recipient recipient

(consisting (consisting

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BRIEF BRIEF

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Arthur Arthur

telephone telephone

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Laboratories Laboratories

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was was

television television finest finest

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TELEPHONE TELEPHONE

1 1 -

created created

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Bell Bell

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laser laser

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importance importance

1.8 1.8 played played

effect. effect.

scientists scientists

awarded awarded

in in

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to to

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semiconductors semiconductors

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TELSTARR TELSTARR

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COMMUNICATIONS COMMUNICATIONS

OF OF

28 28

1. 1.

HISTORY HISTORY

BRIEF BRIEF

1 1 - CH. CH. CH. 1 - BRIEF HISTORY OF COMMUNICATIONS

Communications achievements which have come from Bell Laboratories include: two-way transoceanic radio­ telephone service, the coaxial cable, microwave radio relay systems, the nationwide television network, over-the-horizon microwave transmission, transoceanic telephone cable systems, direct distance dialing, and electronic switching systems. The concept of communications by satellite was first. proposed scientifically by Dr. John R. Pierce of Bell Laboratories. Later, the TELSTAR experimental communica­ tions satellite, which stirred the world when it first spanned the Atlantic with live television in 1962, was engineered, constructed, and successfully tested by Bell Laboratories development engineers. They continued their experiments with the second TELSTAR satellite, which was put into orbit in 1963. 1.9 NEW DEVELOPMENTS A. HOLOGRAPHY Recently, the Bell Telephone Laboratories have been pioneering in Holography which holds great potential for important communications functions. Holography, sometimes called "lenseless photography!! of "wavefront reconstruction photography' 1 is a way of recording the unfocused light reflected or transmitted by an object or objects. The recording, called a hologram, is usually made by exposing a photographic plate to light reflected from a subject and a reference source. The subject and the reference source (often a mirror) are illuminated with laser light. Two aspects of holography that are of primary interest at the Laboratories are: 1. The recording and transmitting of pictoral infor­ mation, including possible uses in PICTUREPHONE and television services; especially, the three dimensional imaging capability of holography.

2. Utilization as a memory device. Holography is still in its infancy. The advent of the laser, with its intense, coherent output (light waves) has given great impetus to its progress. Its potential however, in the final analysis, to the communications media must be evaluated in terms of its economic feasibility.

1.29

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Dr. William 0. Baker - Vice President, Research: ''In the coming years we must prepare to anticipate and meet customer needs for communications facili­ ties of ever-increasing quality and quantity ••. which will involve the transmission of new magnitudes of communications, including intermixed batches of data, works and graphics beyond anything conceived hitherto •.•• "The new technology should enable us to enhance the usefulness of all our service offerings.''

1.32