In Omaha, Nebraska, half-way across the continent and about forty hours
from Boston by fast train, a man sits comfortably in his office chair
and, with no more exertion than is required to lift a portable receiver
off his desk, talks every day to his representative in the chief New
England city. The man in Boston hears his chief's voice and can
recognise the peculiarities in it just as if he stood in the same room
with him. The man in Nebraska, speaking in an ordinary conversational
tone, can be heard perfectly well in Boston, 1,400 miles away.
This is the longest talk on record--that is, it is the longest
continuous telephone line in steady and constant use, though the human
voice has been carried even greater distances with the aid of this
wonderful instrument.
The telephone is so common that no one stops to consider the wonder of
it, and not one person in a hundred can tell how it works.
At this time, when the telephone is as necessary as pen and ink, it is
hard to realise a time when men could not speak to one another from a
distance, yet a little more than a quarter of a century ago the genius
who invented it first conceived the great idea.
Sometimes an inventor is a prophet: he sees in advance how his idea,
perfected and in universal use, will change things, establish new
manners and customs, new laws and new methods. Alexander Graham Bell was
one of these prophetic inventors--the telephone was his invention, not
his discovery. He first got the idea and then sought a way to make it
practical. If you put yourself in his place, forget what has been
accomplished, and put out of mind how the voice is transmitted from
place to place by the slender wire, it would be impossible even then to
realise how much in the dark Professor Bell was in 1874.
The human speaking voice is full of changes; unlike the notes from a
musical instrument, there is no uniformity in it; the rise and fall of
inflection, the varying sound of the vowels and consonants, the
combinations of words and syllables--each produces a different
vibration and different tone. To devise an instrument that would
receive all these varying tones and inflections and change them into
some other form of energy so that they could be passed over a wire, and
then change them back to their original form, reproducing each sound and
every peculiarity of the voice of the speaker in the ear of the hearer,
was the task that Professor Bell set for himself. Just as you would sit
down to add up a big column of figures, knowing that sooner or later you
would get the correct answer, so he set himself to work out this problem
in invention. The result of his study and determination is the
telephones we use to-day. Many improvements have been invented by other
men--Berliner, Edison, Blake, and others--but the idea and the working
out of the principle is due to Professor Bell.
[Illustration: "CENTRAL" TELEPHONE OPERATORS AT WORK
Since tiny lights have taken the place of bells to indicate the calls of
subscribers the central stations are quiet except for the low hum of
carefully modulated voices. The women standing behind the seated
operators are inspectors. They watch for mistakes and disturbances of
any kind.]
Every telephone receiver and transmitter has a mouth-and ear-piece to
receive or throw out the sound, a thin round sheet of lacquered
metal--called a diaphragm, and an electromagnet; together they reproduce
human speech. An electric current from a battery or from the central
station flows continuously through the wires wound round the
electromagnet in receiving and transmitting instruments, so when you
speak into the black mouthpiece of the wall or desk receiver the
vibrations strike against the thin sheet-iron diaphragm at the small end
of the mouthpiece; the sound waves of the voice make it vibrate to a
greater or less degree; the diaphragm is placed so that the core of the
electromagnet is close to it, and as it vibrates the iron in it
produces undulations (by induction) in the current which is flowing
through the wires wound round the soft iron centre of the magnet. The
wires of the coil are connected with the lines that go to the receiving
telephone, so that this undulating current, coiling round the core of
the magnet in the receiver, attracts and repels the iron of the
diaphragm in it, and it vibrates just as the transmitter diaphragm did
when spoken into; the undulating current is translated by it into words
and sentences that have all the peculiarities of the original. And so
when speaking into a telephone your voice is converted into undulations
or waves in an electric current conveyed with incredible swiftness to
the receiving instrument, and these are translated back into the
vibrations that produce speech. This is really what takes place when you
talk over a toy telephone made by a string stretched between the two tin
mouth-pieces held at opposite sides of the room, with the difference
that in the telephone the vibrations are carried electrically, while the
toy carries them mechanically and not nearly so perfectly.
For once the world realised immediately the importance of a
revolutionising invention, and telephone stations soon began to be
established in the large cities. Quicker than the telegraph, for there
was no need of an operator to translate the message, and more accurate,
for if spoken clearly the words could be as clearly understood, the
telephone service spread rapidly. Lines stretched farther and farther
out from the central stations in the cities as improvements were
invented, until the outlying wires of one town reached the outstretched
lines of another, and then communication between town and town was
established. Then two distant cities talked to each other through an
intermediate town, and long-distance telephony was established. To-day
special lines are built to carry long-distance messages from one great
city to another, and these direct lines are used entirely except when
storms break through or the rush of business makes the roundabout route
through intermediate cities necessary.
As the nerves reaching from your finger-tips, from your ears, your eyes,
and every portion of your body come to a focus in your brain and carry
information to it about the things you taste, see, hear, feel, and
smell, so the wires of a telephone system come together at the central
station. And as it is necessary for your right hand to communicate with
your left through your brain, so it is necessary for one telephone
subscriber to connect through the central station with another
subscriber.
The telephone has become a necessity of modern life, so that if through
some means all the systems were destroyed business would be, for a time
at least, paralysed. It is the perfection of the devices for connecting
one subscriber with another, and for despatching the vast number of
messages and calls at "central," that make modern telephony possible.
To handle the great number of spoken messages that are sent over the
telephone wires of a great city it is necessary to divide the territory
into districts, which vary in size according to the number of
subscribers in them. Where the telephones are thickly installed the
districts are smaller than in sections that are more sparsely settled.
Then all the telephone wires of a certain district converge at a central
station, and each pair of wires is connected with its own particular
switch at the switchboard of the station. That is simple enough; but
when you come to consider that every subscriber must be so connected
that he can be put into communication with every other subscriber, not
only in his own section but also with every subscriber throughout the
city, it will be seen that the switchboard at central is as marvellous
as it is complicated. Some of the busy stations in New York have to take
care of 6,000 or more subscribers and 10,000 telephone instruments,
while the city proper is criss-crossed with more than 60,000 lines
bearing messages from more than 100,000 "'phones." Just think of the
babel entering the branch centrals that has to be straightened out and
each separate series of voice undulations sent on its proper way, to be
translated into speech again and poured into the proper ear. It is no
wonder, then, that it has been found necessary to establish a school for
telephone girls where they can be taught how to untangle the snarl and
handle the vast, complicated system. In these schools the operators go
through a regular course lasting a month. They listen to lectures and
work out the instructions given them at a practice switchboard that is
exactly like the service switchboard, except that the wires do not go
outside of the building, but connect with the instructor's desk; the
instructor calls up the pupils and sends messages in just the same way
that the subscribers call "central" in the regular service.
At the terminal station of a great railroad, in the midst of a network
of shining rails, stands the switchman's tower. By means of steel levers
the man in his tower can throw his different switches and open one track
to a train and close another; by means of various signals the switchman
can tell if any given line is clear or if his levers do their work
properly.
A telephone system may be likened, in a measure, to a complicated
railroad line: the trunk wires to subscribers are like the tracks of the
railroad, and the central station may be compared to the switch tower,
while the central operators are like the switchmen. It is the central
girls' business to see that connections are made quickly and correctly,
that no lines are tied up unnecessarily, that messages are properly
charged to the right persons, that in case of a break in a line the
messages are switched round the trouble, and above all that there shall
be no delay.
When you take your receiver off the hook a tiny electric bulb glows
opposite the brass-lined hole that is marked with your number on the
switchboard of your central, and the telephone girl knows that you are
ready to send in a call--the flash of the little light is a signal to
her that you want to be connected with some other subscriber. Whereupon,
she inserts in your connection a brass plug to which a flexible wire is
attached, and then opens a little lever which connects her with your
circuit. Then she speaks into a kind of inverted horn which projects
from a transmitter that hangs round her neck and asks: "Number, please?"
You answer with the number, which she hears through the receiver
strapped to her head and ear. After repeating the number the "hello"
girl proceeds to make the connection. If the number required is in the
same section of the city she simply reaches for the hole or connection
which corresponds with it, with another brass plug, the twin of the one
that is already inserted in your connection, and touches the brass
lining with the plug. All the connections to each central station are so
arranged and duplicated that they are within the reach of each operator.
If the line is already "busy" a slight buzz is heard, not only by
"central," but by the subscriber also if he listens; "central" notifies
and then disconnects you. If the line is clear the twin plug is thrust
into the opening, and at the same time "central" presses a button, which
either rings a bell or causes a drop to fall in the private exchange
station of the party you wish to talk to. The moment the new connection
is made and the party you wish to talk to takes off the receiver from
his hook, a second light glows beside yours, and continues to glow as
long as the receiver remains off. The two little lamps are a signal to
"central" that the connection is properly made and she can then attend
to some other call. When your conversation is finished and your
receivers are hung up the little lights go out. That signals "central"
again, and she withdraws the plug from both holes and pushes another
button, which connects with a meter made like a bicycle cyclometer. This
little instrument records your call (a meter is provided for each
subscriber) and at the same time lights the two tiny lamps again--a
signal to the inspector, if one happens to be watching, that the call is
properly recorded. All this takes long to read, but it is done in the
twinkling of an eye. "Central's" hands are both free, and by long
practice and close attention she is able to make and break connections
with marvellous rapidity, it being quite an ordinary thing for an
operator in a busy section to make ten connections a minute, while in
an emergency this rate is greatly increased.
[Illustration: "CENTRAL" MAKING CONNECTIONS
The front of a small section of a central-station switchboard. Each dot
on the face of the blackboard is a subscriber's connection. The cords
connect one subscriber with another. The switches throwing in the
operator's "phone", and the pilot lamps showing when a subscriber wishes
a connection, are set in the table or shelf before her.]
The call of one subscriber for another number in the same section, as
described above--for instance, the call of 4341 Eighteenth Street for
2165 Eighteenth Street--is the easiest connection that "central" has to
make.
As it is impossible for each branch exchange to be connected with every
individual line in a great city, when a subscriber of one exchange
wishes to talk with a subscriber of another, two central operators are
required to make the connection. If No. 4341 Eighteenth Street wants to
talk to 1748 Cortlandt Street, for instance, the Eighteenth Street
central who gets the 4341 call makes a connection with the operator at
Cortlandt Street and asks for No. 1748. The Cortlandt Street operator
goes through the operation of testing to see if 1748 is busy, and if not
she assigns a wire connecting the two exchanges, whereupon in Eighteenth
Street one plug is put in 4341 switch hole; the twin plug is put into
the switch hole connecting with the wire to Cortlandt Street; at
Cortlandt Street the same thing is done with No. 1748 pair of plugs. The
lights glow in both exchanges, notifying the operators when the
conversation is begun and ended, and the operator of Eighteenth Street
"central" makes the record in the same way as she does when both numbers
are in her own district.
Besides the calls for numbers within the cities there are the
out-of-town calls. In this case central simply makes connection with
"Long Distance," which is a separate company, though allied with the
city companies. "Long Distance" makes the connection in much the same
way as the branch city exchanges. As the charges for long-distance calls
depend on the length of the conversation, so the connection is made by
an operator whose business it is to make a record of the length in
minutes of the conversation and the place with which the city subscriber
is connected. An automatic time stamp accomplishes this without
possibility of error.
Sometimes the calls come from a pay station, in which case a record must
be kept of the time occupied. This kind of call is indicated by the glow
of a red light instead of a white one, and so "central" is warned to
keep track, and the supervisors or monitors who constantly pass to and
fro can note the kind of calls that come in, and so keep tab on the
operators.
Other coloured lights indicate that the chief operator wishes to send
out a general order and wishes all operators to listen. Another
indicates that there is trouble somewhere on the line which needs the
attention of the wire chief and repair department.
[Illustration: THE BACK OF A TELEPHONE SWITCHBOARD
A section of one of several central station switchboards necessary to
carry the telephone traffic of a great city.]
The switchboards themselves are made of hard, black rubber, and are
honeycombed with innumerable holes, each of which is connected with a
subscriber. Below the switchboard is a broad shelf in which are set the
miniature lamps and from which project the brass plugs in rows. The
flexible cords containing the connecting wires are weighted and hang
below, so that when a plug is pulled out of a socket and dropped it
slides back automatically to its proper place, ready for use.
Many subscribers nowadays have their own private exchanges and several
lines running to central. Perhaps No. 4341 Eighteenth Street, for
instance, has 4342 and 4344 as well. This is indicated on the
switchboard by a line of red or white drawn under the three
switch-holes, so that central, finding one line busy, may be able to
make connection with one of the other two, the line underneath showing
at a glance which numbers belong to that particular subscriber.
If a subscriber is away temporarily, a plug of one colour is inserted
in his socket, or if he is behind in his payments to the company a plug
of another colour is put in, and if the service to his house is
discontinued still another plug notifies the operator of the fact, and
it remains there until that number is assigned to a new subscriber.
The operators sit before the switchboard in high swivel chairs in a long
row, with their backs to the centre of the room.
From the rear it looks as if they were weaving some intricate fabric
that unravels as fast as it is woven. Their hands move almost faster
than the eye can follow, and the patterns made by the criss-crossed
cords of the connecting plugs are constantly changing, varying from
minute to minute as the colours in a kaleido-scope form new designs with
every turn of the handle.
Into the exchange pour all the throbbing messages of a great city.
Business propositions, political deals, scientific talks, and words of
comfort to the troubled, cross and recross each other over the black
switchboard. The wonder is that each message reaches the ear it was
meant for, and that all complications, no matter how knotty, are
immediately unravelled.
In the cities the telephone is a necessity. Business engagements are
made and contracts consummated; brokers keep in touch with their
associates on the floors of the exchanges; the patrolmen of the police
force keep their chief informed of their movements and the state of the
districts under their care; alarms of fire are telephoned to the
fire-engine houses, and calls for ambulances bring the swift wagons on
their errands of mercy; even wreckers telephone to their divers on the
bottom of the bay, and undulating electrical messages travel to the tops
of towering sky-scrapers.
[Illustration: A FEW TELEPHONE TRUNK WIRES
This shows a small section of a complicated telephone switchboard.]
In Europe it is possible to hear the latest opera by paying a small fee
and putting a receiver to your ear, and so also may lazy people and
invalids hear the latest news without getting out of bed.
The farmers of the West and in eastern States, too, have learned to use
the barbed wire that fences off their fields as a means of communicating
with one another and with distant parts of their own property.
Mr. Pupin has invented an apparatus by which he hopes to greatly extend
the distance over which men may talk, and it has even been suggested
that Uncle Sam and John Bull may in the future swap stories over a
transatlantic telephone line.
The marvels accomplished suggest the possible marvels to come.
Automatic exchanges, whereby the central telephone operator is done away
with, is one of the things that inventors are now at work on.
The one thing that prevents an unlimited use of the telephone is the
expensive wires and the still more expensive work of putting them
underground or stringing them overhead. So the capping of the climax of
the wonders of the telephone would be wireless telephony, each
instrument being so attuned that the undulations would respond only to
the corresponding instrument. This is one of the problems that inventors
are even now working upon, and it may be that wireless telephones will
be in actual operation not many years after this appears in print.