the dancing spot of light it is passed on over rollers through
developing and fixing chemical baths; so that the receiving of
messages is purely automatic.
The reader can judge for himself the results of this ingenious system
as shown in a short section of a message transmitted by Mr. Pollak.
The words shown actually occupied two seconds in transmission. They
are beautifully clear.
It is said that by the aid of a special “multiplex” device thirty sets
of Pollak-Virag apparatus can be used simultaneously on a line! The
reader will be able, by the aid of a small calculation, to arrive at
some interesting figures as regards their united output.
THE TELEPHONE.
A common enough sight in any large town is a great sheaf of fine wires
running across the streets and over the houses. If you traced their
career in one direction you would find that they suddenly terminate,
or rather combine into cables, and disappear into the recesses of a
house, which is the Telephone Exchange. If you tracked them the other
way your experience would be varied enough. Some wires would lead you
into public institutions, some into offices, some into snug rooms in
private houses. At one time your journey would end in the town, at
another you would find yourself roaming far into the country, through
green fields and leafy lanes until at last you ran the wire to earth
in some large mansion standing in a lordly park. Perhaps you might
have to travel hundreds of miles, having struck a “trunk” line
connecting two important cities; or you might even be called upon to
turn fish and plunge beneath the sea for a while, groping your way
along a submarine cable.
In addition to the visible overhead wires that traverse a town there
are many led underground through special conduits. And many telephone
wires never come out of doors at all, their object being to furnish
communication between the rooms of the same house. The telephone and
its friend, the electric-bell, are now a regular part of the equipment
of any large premises. The master of the house goes to his telephone
when he wishes to address the cook or the steward, or the
head-gardener or the coachman. It saves time and labour.
Should he desire to speak to his town-offices he will, unless
connected direct, “ring up” the Exchange, into which, as we have seen,
flow all the wires of the subscribers to the telephone system of that
district. The ringing-up is usually done by rapidly turning a handle
which works an electric magnet and rings a bell in the Exchange. The
operator there, generally a girl, demands the number of the person
with whom the ringer wants to speak, rings up that number, and
connects the wires of the two parties.
In some exchanges, _e.g._ the new Post-Office telephone exchanges, the
place of electric-bells is taken by lamps, to the great advantage of
the operators, whose ears are thus freed from perpetual jangling. The
action of unhooking the telephone receiver at the subscriber’s end
sends a current into a relay which closes the circuit of an electric
lamp opposite the subscriber’s number in the exchange. Similarly, when
the conversation is completed the action of hanging up the receiver
again lights another lamp of a different colour, given the exchange
warning that the wires are free again.
In America, the country of automatic appliances, the operator is
sometimes entirely dispensed with. A subscriber is able, by means of
a mechanical contrivance, to put himself in communication with any
other subscriber unless that subscriber is engaged, in which case a
dial records the fact.
The popularity of the telephone may be judged from the fact that in
1901 the National Telephone Company’s system transmitted over 807
millions of messages, as compared with 89 millions of telegrams sent
over the Post Office wires. In America and Germany, however, the
telephone is even more universally employed than in England. In the
thinly populated prairies of West America the farm-houses are often
connected with a central station many miles off, from which they
receive news of the outer world and are able to keep in touch with one
another. We are not, perhaps, as a nation sufficiently alive to the
advantages of an efficient telephone system; and on this account many
districts remain telephoneless because sufficient subscribers cannot
be found to guarantee use of a system if established. It has been
seriously urged that much of our country depopulation might be
counteracted by a universal telephone service, which would enable
people to live at a distance from the towns and yet be in close
contact with them. At present, for the sake of convenience and ease of
“getting at” clients and customers, many business men prefer to have
their homes just outside the towns where their business is. A cheap
and efficient service open to every one would do away with a great
deal of travelling that is necessary under existing circumstances,
and by making it less important to live near a town allow people to
return to the country.
Even Norway has a good telephone system. The telegraph is little used
in the more thinly inhabited districts, but the telephone may be found
in most unexpected places, in little villages hidden in the recesses
of the fiords. Switzerland, another mountainous country, but very
go-ahead in all electrical matters, is noted for the cheapness of its
telephone services. At Berne or Geneva a subscriber pays £4 the first
year, £2, 12s. the second year, and but £1, 12s. the third. Contrast
these charges with those of New York, where £15, 10s. to £49, 10s. is
levied annually according to service.
The telephone as a public benefactor is seen at its best at
Buda-Pesth, the twin-capital of Hungary. In 1893, one Herr Theodore
Buschgasch founded in that city a “newspaper”--if so it may be
called--worked entirely on the telephone. The publishing office was a
telephone exchange; the wires and instruments took the place of
printed matter. The subscribers were to be informed entirely by ear of
the news of the day.
The _Telefon Hirmondo_ or “Telephonic Newsteller,” as the “paper” was
named, has more than six thousand subscribers, who enjoy their
telephones for the very small payment of eighteen florins, or about a
penny a day, for twelve hours a day.
News is collected at the central office in the usual journalistic way
by telephone, telegraph, and reporters. It is printed by lithography
on strips of paper six inches wide and two feet long. These strips are
handed to “stentors,” or men with powerful and trained voices, who
read the contents to transmitting instruments in the offices, whence
it flies in all directions to the ears of the subscribers.
These last know exactly when to listen and what description of
information they will hear, for each has over his receiver a programme
which is rigidly adhered to. It must be explained at once that the
_Telefon Hirmondo_ is more than a mere newspaper, for it adds to its
practical use as a first-class journal that of entertainer, lecturer,
preacher, actor, political speaker, musician. The _Telefon_ offices
are connected by wire with the theatres, churches, and public halls,
drawing from them by means of special receivers the sounds that are
going on there, and transmitting them again over the wires to the
thousands of subscribers. The Buda-Pesthian has therefore only to
consult his programme to see when he will be in touch with his
favourite actor or preacher. The ladies know just when to expect the
latest hints about the fashions of the day. Nor are the children
forgotten, for a special period is set aside weekly for their
entertainment in the shape of lectures or concerts.
The advertising fiend, too, must have his say, though he pays dearly
for it. On payment of a florin the stentors will shout the virtues of
his wares for a space of twelve seconds. The advertising periods are
sandwiched in between items of news, so that the subscriber is bound
to hear the advertisements unless he is willing to risk missing some
of the news if he hangs up his receiver until the “puff” is finished.
Thanks to the _Telefon Hirmondo_ the preacher, actor, or singer is
obliged to calculate his popularity less by the condition of the seats
in front of him than by the number of telephones in use while he is
performing his part. On the other hand, the subscriber is spared a
vast amount of walking, waiting, cab-hire, and expense generally. In
fact, if the principle is much further developed, we shall begin to
doubt whether a Buda-Pesthian will be able to discover reasons for
getting out of bed at all if the receiver hanging within reach of his
hand is the entrance to so many places of delight. Will he become a
very lazy person; and what will be the effect on his entertainers when
they find themselves facing benches that are used less every day? Will
the sight of a row of telephone trumpets rouse the future Liddon,
Patti, Irving, or Gladstone to excel themselves? It seems rather
doubtful. Telephones cannot look interested or applaud.
What is inside the simple-looking receiver that hangs on the wall
beside a small mahogany case, or rests horizontally on a couple of
crooks over the case? In the older type of instrument the transmitter
and receiver are separate, the former fixed in front of the case, the
latter, of course, movable so that it can be applied to the ear. But
improved patterns have transmitter and receiver in a single movable
handle, so shaped that the earpiece is by the ear while the
mouthpiece curves round opposite the mouth. By pressing a small lever
with the fingers the one or the other is brought into action when
required.
The construction of the instrument, of which we are at first a little
afraid, and with which we later on learn to become rather angry, is in
its general lines simple enough. The first practical telephone,
constructed in 1876 by Graham Bell, a Scotchman, consisted of a long
wooden or ebonite handle down the centre of which ran a permanent
bar-magnet, having at one end a small coil of fine insulated wire
wound about it The ends of the wire coil are led through the handles
to two terminals for connection with the line wires. At a very short
distance from the wire-wound pole of the magnet is firmly fixed by its
edges a thin circular iron plate, covered by a funnel-shaped
mouthpiece.
The iron plate is, when at rest, concave, its centre being attracted
towards the pole of the magnet. When any one speaks into the
mouthpiece the sound waves agitate the diaphragm (or plate), causing
its centre to move inwards and outwards. The movements of the
diaphragm affect the magnetism of the magnet, sometimes strengthening
it, sometimes weakening it, and consequently exciting electric
currents of varying strength in the wire coil. These currents passing
through the line wires to a similar telephone excite the coil in it,
and in turn affect the magnetism of the distant magnet, which
attracts or releases the diaphragm near its pole, causing undulations
of the air exactly resembling those set up by the speaker’s words. To
render the telephone powerful enough to make conversation possible
over long distances it was found advisable to substitute for the one
telephone a special transmitter, and to insert in the circuit a
battery giving a much stronger current than could possibly be excited
by the magnet in the telephone at the speaker’s end.
Edison in 1877 invented a special transmitter made of carbon. He
discovered that the harder two faces of carbon are pressed together
the more readily will they allow current to pass; the reason probably
being that the points of contact increase in number and afford more
bridges for the current.
Accordingly his transmitter contains a small disc of lampblack (a form
of carbon) connected to the diaphragm, and another carbon or platinum
disc against which the first is driven with varying force by the
vibrations of the voice.
The Edison transmitter is therefore in idea only a modification of the
microphone. It acts as a _regulator_ of current, in distinction to the
Bell telephone, which is only an _exciter_ of current. Modern forms of
telephones unite the Edison transmitter with the Bell receiver.
The latter is extremely sensitive to electric currents, detecting them
even when of the minutest power. We have seen that Marconi used a
telephone in his famous transatlantic experiments to distinguish the
signals sent from Cornwall. A telephone may be used with an “earth
return” instead of a second wire; but as this exposes it to stray
currents by induction from other wires carried on the same poles or
from the earth itself, it is now usual to use two wires, completing
the metallic circuit. Even so a subscriber is liable to overhear
conversations on wires neighbouring his own; the writer has lively
recollections of first receiving news of the relief of Ladysmith in
this manner.
Owing to the self-induction of wires in submarine cables and the
consequent difficulty of forcing currents through them, the telephone
is at present not used in connection with submarine lines of more than
a very moderate length. England has, however, been connected with
France by a telephone cable from St. Margaret’s Bay to Sangatte, 23
miles; and Scotland with Ireland, Stranraer to Donaghadee, 26 miles.
The former cable enables speech between London and Marseilles, a
distance of 900 miles; and the latter makes it possible to speak from
London to Dublin _viâ_ Glasgow. The longest direct line in existence
is that between New York and Chicago, the complete circuit of which
uses 1900 miles of stout copper wire, raised above the ground on poles
35 feet high.
The efficiency of the telephone on a well laid system is so great that
it makes very little difference whether the persons talking with one
another are 50 or 500 miles apart. There is no reason why a
Cape-to-Cairo telephone should not put the two extremities of Africa
in clear vocal communication. We may even live to see the day when a
London business man will be able to talk with his agent in Sydney,
Melbourne, or Wellington.
A step towards this last achievement has been taken by M. Germain, a
French electrician, who has patented a telephone which can be used
with stronger currents than are possible in ordinary telephones;
thereby, of course, increasing the range of speech on submarine
cables.
The telephone that we generally use has a transmitter which permits
but a small portion of the battery power to pass into the wires, owing
to the resistance of the carbon diaphragm. The weakness of the current
is to a great extent compensated by the exceedingly delicate nature of
the receiver.
M. Germain has reversed the conditions with a transmitter that allows
a very high percentage of the current to flow into the wires, and a
comparatively insensitive receiver. The result is a “loud-speaking
telephone”--not a novelty, for Edison invented one as long ago as
1877--which is capable of reproducing speech in a wonderfully powerful
fashion.
M. Germain, with the help of special tubular receivers, has actually
sent messages through a line having the same resistance as that of the
London-Paris line, so audibly that the words could be heard fifteen
yards from the receiver in the open air!
The Telephone
WIRELESS TELEPHONY.
In days when wireless telegraphy is occupying such a great deal of the
world’s attention, it is not likely to cause much astonishment in the
reader to learn that wireless transmission of _speech_ over
considerable distances is an accomplished fact. We have already
mentioned (see “Wireless Telegraphy”) that by means of parallel
systems of wires Sir William Preece bridged a large air-gap, and
induced in the one sounds imparted to the other.
Since then two other methods have been introduced; and as a preface to
the mention of the first we may say a few words about Graham Bell’s
_Photophone_.
In this instrument _light_ is made to do the work of a metal
connection between speaker and listener. Professor Bell, in arranging
the Photophone, used a mouthpiece as in his electric telephone, but
instead of a diaphragm working in front of a magnet to set up electric
impulses along a wire he employed a mirror of very thin glass,
silvered on one side. The effect of sound on this mirror was to cause
rapid alterations of its shape from concave to convex, and consequent
variations of its reflecting power. A strong beam of light was
concentrated on the centre of the mirror through a lens, and reflected
by the mirror at an angle through another lens in the direction of the
receiving instrument. The receiver consisted of a parabolic reflector
to catch the rays and focus them on a selenium cell connected by an
electric circuit with an ordinary telephone earpiece.
On delivering a message into the mouthpiece the speaker would, by
agitating the mirror, send a succession of light waves of varying
intensity towards the distant selenium cell. Selenium has the peculiar
property of offering less resistance to electrical currents when light
is thrown upon it than when it is in darkness: and the more intense is
the light the less is the obstruction it affords. The light-waves from
the mirror, therefore, constantly alter its capacity as a conductor,
allowing currents to pass through the telephone with varying power.
In this way Professor Bell bridged 800 yards of space; over which he
sent, besides articulate words, musical notes, using for the latter
purpose a revolving perforated disc to interrupt a constant beam of
light a certain number of times per second. As the speed of the disc
increased the rate of the light-flashes increased also, and produced
in the selenium cell the same number of passages to the electric
current, converted into a musical note by the receiver. So that by
means of mechanical apparatus a “playful sunbeam” could literally be
compelled to play a tune.
From the Photophone we pass to another method of sound transmission by
light, with which is connected the name of Mr. Hammond V. Hayes of
Boston, Massachusetts. It is embodied in the Radiophone, or the
Ray-speaker, for it makes strong rays of light carry the human voice.
Luminous bodies give off heat. As the light increases, so as a general
rule does the heat also. At present we are unable to create strong
light without having recourse to heat to help us, since we do not know
how to cause other vibrations of sufficient rapidity to yield the
sensation of light. But we can produce heat directly, and heat will
set atoms in motion, and the ether too, giving us light, but taking as
reward a great deal of the energy exerted. Now, the electric arc of a
searchlight produces a large amount of light _and_ heat. The light is
felt by the eye at a distance of many miles, but the body is not
sensitive enough to be aware of the heat emanating from the same
source. Mr. Hayes has, however, found the heat accompanying a
searchlight beam quite sufficient to affect a mechanical “nerve” in a
far-away telephone receiver.
The transmitting apparatus is a searchlight, through the back of which
run four pairs of wires connected with a telephone mouthpiece after
passing through a switch and resistance-box or regulator. The receiver
is a concave mirror, in the focus of which is a tapering glass bulb,
half filled with carbonised filament very sensitive to heat. The
tapering end of the bulb projects through the back of the mirror into
an ear tube.
If a message is to be transmitted the would-be speaker turns his
searchlight in the direction of the person with whom he wishes to
converse, and makes the proper signals. On seeing them the other
presents his mirror to the beam and listens.
The speaker’s voice takes control of the searchlight beam. The louder
the sound the more brilliantly glows the electric arc; the stronger
becomes the beam, the greater is the amount of heat passed on to the
mirror and gathered on the sensitive bulb. The filament inside
expands. The tapering point communicates the fact to the earpiece.
This operation being repeated many times a second the earpiece fills
with sound, in which all the modulations of the far-distant voice are
easily distinguishable.
Two sets of the apparatus above described are necessary for a
conversation, the functions of the searchlight and the bulb not being
reversible. But inasmuch as all large steamers carry searchlights the
necessary installation may be completed at a small expense. Mr. Hayes’
invention promises to be a rival to wireless telegraphy over
comparatively short distances. It can be relied upon in all weathers,
and is a fast method of communication. Like the photophone it
illustrates the inter-relationship of the phenomena of Sound, Light,
and Heat, and the readiness with which they may be combined to attain
an end.
Next we turn from air to earth, and to the consideration of the work
of Mr. A. F. Collins of Philadelphia. This electrician merely makes
use of the currents flowing in all directions through the earth, and
those excited by an electric battery connected with earth. The outfit
requisite for sending wireless spoken messages consists of a couple of
convenient stands, as many storage batteries, sets of coils, and
receiving and transmitting instruments.
The action of the transmitter is to send from the battery a series of
currents through the coils, which transmit them, greatly intensified,
to the earth by means of a wire connected with a buried wire-screen.
The electric disturbances set up in the earth travel in all
directions, and strike a similar screen buried beneath the receiving
instrument, where the currents affect the delicate diaphragm of the
telephone earpiece.
The system is, in fact, upon all fours with Mr. Marconi’s, the
distinguishing feature being that the ether of the atmosphere is used
in the latter case, that of the earth in the former. The intensity
coils are common to both; the buried screens are the counterpart of
the aërial kites or balloons; the telephone transmitter corresponds to
the telegraphic transmitting key; the earpiece to the coherer and
relay. No doubt in time Mr. Collins will “tune” his instruments, so
obtaining below ground the same sympathetic electric vibrations which
Mr. Marconi, Professor Lodge, or others have employed to clothe their
aërial messages in secrecy.
THE PHONOGRAPH.
Even if Thomas Edison had not done wonders with electric lighting,
telephones, electric torpedoes, new processes for separating iron from
its ore, telegraphy, animated photography, and other things too
numerous to mention, he would still have made for himself an enduring
name as the inventor of the Phonograph. He has fitly been called the
“Wizard of the West” from his genius for conjuring up out of what
would appear to the multitude most unpromising materials startling
scientific marvels, among which none is more truly wizard-like than
the instrument that is as receptive of sound as the human ear, and of
illimitable reproducing power. By virtue of its elfishly human
characteristic, articulate speech, it occupies, and always will
occupy, a very high position as a mechanical wonder. When listening to
a telephone we are aware of the fact that the sounds are immediate
reproductions of a living person’s voice, speaking at the moment and
at a definite distance from us; but the phonographic utterances are
those of a voice perhaps stilled for ever, and the difference adds
romance to the speaking machine.
The Phonograph was born in 1876. As we may imagine, its appearance
created a stir. A contributor to the _Times_ wrote in 1877: “Not many
weeks have passed since we were startled by the announcement that we
could converse audibly with each other, although hundreds of miles
apart, by means of so many miles of wire with a little electric magnet
at each end.