Method and Apparatus for Reproducing Pictures and the like at a Distance by Means of Electricity.
Year: 1897

page_text: PROVISIONAL SPECIFICATION.
Method and Apparatus for Reproducing Pictures and the like at
a Distance by Means of Electricity.
We, JAN SZCZEPANIK, Engineer, and LUDWIG KLEINBERG, Banker, both of
I Bartensteinstrasse 16, Vienna, Austria, do hereby declare the nature of this invention
to be as follows:-
This invention relates to a method and an apparatus for transmitting a picture or
representation of an object (hereinafter called the picture) and rendering it visible
in its natural colours at a distant place by electrical means.
According to this method the picture that is to be rendered visible at a distance is
broken up into a number of points and the several rays corresponding to these points
are combined together again to form a picture by means of two pairs of mirrors
placed at the transmitting and receiving stations and oscillating synchronously; for
the purpose of transmission, the differences of light of the rays of light passing from
the picture-points obtained by breaking up being first converted into differences of
current, and the latter being then transmitted through the line conductor to the
receiving station and there re-converted into differences of light.
The conversion of the light-rays into electrical current impulses can be effected in
various known ways. If the conversion of the several points of the picture that is to
be rendered visible take place in sufficiently rapid succession, the eye of the observer
will receive the impression of the entire picture, and if the picture be reproduced
repeatedly in sufficiently rapid succession, the observer will receive the impression of
a permanent picture, the subject of which may appear to be at rest or in motion
according to the nature of the successive pictures thus "telelectroscoped."
A suitable arrangement of apparatus for carrying out this method comprises
therefore two main portions-viz., the transmitting device and the receiving device
which are connected together by conducting wires or, it may be, by a single wire
only.
In each of the two devices there are arranged two oscillating mirrors which are
moved synchronously by means of electromagnets. As in transmitting the picture
by means of a single conducting wire only one point of the picture situated at the
transinitting-station can be sent at a time, therefore the. mirrors must be so arranged
that in any position and at any instant they will reflect only one of the picture-
points and thus bring each time a ray of definite property or quality into operation
in that portion of the apparatus which converts the differences of light into differences
of electric current.
This portion of the apparatus may be variously constructed according as the
conversion is effected by (a) the variation of the conductivity in consequence of
exposure to light (by using selenium, sulphur, tellurium, soot or lampblack, or other
substance having this property); (b) photoelectricity; (c) thermo-electricity;
(d) radiophonic action; (e) variation of magnetism by exposure to light; or by other
causes.
The rays, which are converted into electric currents of various strengths according

page_text: to the colour of the light emitted from the several picture-points, produce at the
receiving-station a corresponding energizing of an electro-magnet and the consequent
movement of a prism in such a manner that only a ray of similar kind of the light
falling from a source of light on to the prism and becoming decomposed thereby,
can reach the synchronously oscillating mirrors at the receiving station. The
reflecting action of these mirrors is such as to cause the picture-point transmitted to
the eye of the observer to be visible to him at the place and in the colour
corresponding to the point at the transmitting station.
We shall now proceed to describe a particular form of construction of this apparatus,
in which a selenium cell is employed.
Fig. 1 of the accompanying drawings illustrates the general arrangement of the
apparatus (transmitting station and receiving station);
Fig. 2 shows one of the oscillating mirrors;
Fig. 3 shows the electromagnet for moving the mirror ;
Figs. 4 and 5 illustrate, in plan and in vertical section respectively, the selenium
cell employed; and
Figs. 6 to 9 inclusive are diagrams showing different ways of breaking up the
picture that is to be telegraphed.
Each of the four mirrors a is made by coating the reflecting surface of the mirror
with an opaque mass, and by making, by means of a pointed or sharp-edged tool
(needle or knife), a straight scratch or cut, so as to produce a reflecting surface in the
form of a very narrow linear strip. By means of a mirror of this kind, only one line
of the object G under observation is rendered visible, because if the eye is stationary,
only those rays can reach the eye which are reflected at an angle that is equal to the
angle of incidence at which the rays projected from a line of the picture in the same
plane, fall upon the mirror.
The mirror is fixed to an iron plate b which forms the armature of an electro-
magnet E and is provided with pivots C.
By means of the attraction of the armature bin consequence of the action of the
electromagnet E, the mirror a is caused to vibrate or oscillate, and consequently
continually changing lines of the picture under observation become visible, because
the angle of the incident rays and therefore also of the reflected rays is continually
being changed thereby.
Now, for the purpose of breaking up those lines into points, the other mirror a¹
of the transmitting apparatus A, which is likewise operated by an electromagnet E¹,
is arranged on the armature 6' in such a manner that the reflecting lines of the
two mirrors are situated in planes at right angles to each other. Then in a given
mutual position of the two mirrors, only a determined point of the reflecting line
of the first mirror will appear in the second mirror, and therefore only the reflected
ray corresponding to this point will be reflected by the second mirror."
When the two mirrors vibrate on their pivots C, the double reflection causes rays
of different points of the object to fall successively upon a determined part of a
wall w provided in the transmitting apparatus A, and in this manner an endless line
can be formed of the successive points of the picture.
Figs. 6 and 8 illustrate diagrammatically different ways of breaking up the picture
into points k, which follow one another so as to form an endless line K. The
abscissae X of the points k determine the motion of the first mirror, which oscillates
about a horizontal axis, and the ordinates y of the said points determine the alteration
of position of the second mirror, which oscillates about a vertical axis.
The results of the motion of these two mirrors are the endless lines K, of which
the one shown in Fig. 8 is the longest, because the difference between the movements
of the two mirrors is greatest. The greater or less closeness of the succession of
the points in the line K is dependent on this said difference, which therefore
also serves to determine the accuracy of the reproduction of the decomposed
picture.
By this means, during the motion of the mirrors, continually changing rays of light

page_text: emitted from the picture are thrown on to a definite spot on the wall w,
differ from one another as regards intensity and also colour.
which rays
These differences of light have now to be converted into differences of current, in
order to ensure their reproduction at a distant place.
This is, in the example of apparatus shown, advantageously effected with the aid
of a selenium cell S the conductivity of which, as is well known, is considerably
increased by exposure to light, and is also varied in different degrees by the action
of rays of different colours. This selenium cell is arranged behind an aperture o
provided at the place in the wall w where the ray falls that is reflected from the
second mirror a' of the transmitting apparatus. The cell S is included together with
a battery B in a circuit L, which leads to the receiving apparatus A¹, and is there
connected to an electro-magnet E² and also to a small incandescence-lamp l, which is
located on a branch.
When the selenium cell S is not exposed to light, no current passes in the circuit L
because selenium has a very great resistance in the dark. But as soon as a reflected
ray of light falls through the aperture upon the selenium, this resistance becomes
at once diminished to such an extent that a current flows from the battery through
the circuit, energizing the electro-magnet E² and rendering the lamp / incandescent.
As the action of the several rays varies according to their colour, various degrees of
conductivity of the selenium are produced, and consequently battery-currents of
various strengths are sent into the circuit L.
For the purpose of converting the differences of current thus produced, back again
into differences of light, there is arranged on the armature 62 of the electro-magnet E2
a prism p, and in the wall w¹ there is provided an aperture o¹ such that of the light
emitted from the incandescent lamp and decomposed by the prism there can pass
through the aperture only the portion that corresponds in colour to the ray to which
the selenium cell of the transmitting apparatus is exposed at the same moment and
which produces a current of a definite strength corresponding to its colour and thus
brings about a corresponding movement of the armature towards the energized
electro-magnet and consequently a change of position of the prism p.
Instead of the light of the incandescence-lamp direct sunlight may be employed,
which will then enter through a slit o² in the casing and be decomposed by the
prism.
The ray passing through the aperture o¹ of the receiving apparatus for instance,
a blue ray when the selenium cell is exposed to a blue ray-undergoes, in the
same manner but in the opposite direction, a double reflection by means of two
mirrors aa which also oscillate on their pivots c under the action of electro-
magnets E E, and thereby effect the composition of the several successive rays so as
to form a picture or image G¹.
For this purpose all that is necessary is that the mirrors of the two apparatus A
and A' move in perfect synchronism. With this object the two electro-magnets E E
of the mirrors that oscillate about horizontal axes are connected with a battery B¹
by means of a lead L', whilst the electro-magnets E¹ E' of the mirrors that oscillate
about vertical axes are connected with a battery B2 by means of a lead I, and in
each of these battery-circuits there is arranged a current-interrupting device, an,
induction-apparatus, a microphone, or some other device M¹ or M2 by means of
which the current is constantly interrupted or varied in strength.
As the light emitted from the object G into the transmitting apparatus A, acts only
at one point in consequence of the operation and position of the mirrors, the use of
an objective may be dispensed with.
In front of the receiving apparatus A² there may be arranged a photographic
plate upon which the object situated in front of the transmitting apparatus will
appear after a certain time, or the eye itself may be employed as a photographic camera.
in which case the several light-rays are rendered visible upon the retina. The.
impressions of images upon the same are, however, of very short duration and
disappear after 01 to 0.5 of a second. Consequently if the whole of the points of the
original picture be telelectroscoped, the observer will, from this succession of

page_text: photographs produced in the eye, have the consciousness of seeing the entire
picture just as if the whole of the points of the picture were transmitted
simultaneously.
If, before the complete disappearance of the picture, a second, third, and so on
repetition of the picture be transmitted in the same way, the eye will receive the
impression of a permanent picture. If the successively transmitted pictures
correspond to different phases of motion of the object, the impression of a moving
picture can be made on the retina of the eye, exactly as in the case of the strobo-
scope, kinematograph, and the like.
The employment of an objective is of advantage if a large picture is to be trans-
mitted, or if it is to be projected or observed directly to a large scale.
As will be seen, in the described apparatus three batteries B, B¹, and B2 and three
conductors L, L, & I are necessary in order to render its operation possible, the
conductor L, with its battery B, serving for transmitting the picture, and the electro-
magnets conductors L1 and L2, with their batteries, serving for moving the mirrors
synchronously.
For greater distances between the transmitting and receiving places, it is, however,
desirable, on account of the great cost of a plurality of conductors, to do away
with two of them, so that the seeing from a distance and the synchronous move-
ment of the mirrors can be effected with a single wire.
This is, as regards the one electromagnet-conductor, effected by connecting two
corresponding ones of the electromagnets with the conductor L that serves for trans-
mitting the differences of light converted into electric currents.
The two other electromagnets cannot, however, be directly connected with the main
conductor, as otherwise the two mirrors of the transmitting or the receiving
apparatus
us would execute a uniform movement, which would have as a result that
there would always be reflected only a single limited line K in the direction of the
diagonal (as shown in Fig. 9) and there would consequently be transmitted only this
line and not the entire picture. Therefore with the line-conductor L there are
connected two like apparatus (inductors, transformers) and into the secondary
conductors thereof there are inserted the two electro-magnets acting on the mirrors;
thereby the number of the current-oscillations is changed uniformly and the electro-
magnets of each part A and A¹ of the apparatus will produce oscillations differing in
number but proceeding synchronously in the two apparatus.
When employing three conductors, the electro-magnets E E¹ can be used as
microphones acting independently of one another as soon as they are suitably
connected with telephones, the mechanical action on the microphones that takes
place in the case of the ordinary telephone apparatus, being, of course, omitted. The
signal bell may be put into circuit in a manner similar to that of the latter apparatus
and the entire apparatus be accordingly used simultaneously for seeing from a
distance and for speaking from a distance. If one or both of the electro-magnet-
conductors be omitted, the microphone will be omitted in one or both of the
parts of the apparatus (transmitting or receiving station).
To ensure certainty in the operation of the arrangement for a long time, it is
essential to remove the drawback attaching to the hitherto known selenium-cells
serving for different purposes and consisting in that with constant illumination the
selenium loses in sensitiveness to light.
This is attained by using the construction of selenium cell shown in Figs. 4
and 5.
This consists of two concentric brass-rings between which there is put, as a
lining, a thin annular layer 8 of selenium, so that a disc is produced; this can be
displaced in slow rotation about its axist by means of a clockwork (Fig. 1). On
the brass-rings rest two contact-makers u u', which are connected with the battery B
or with the line-conductor L. The disc is placed in a part of the apparatus shut off
from the interior by the wall w, so that during its rotation only a small portion of the
selenium rings can be struck by the ray passing in through the opening o, whilst
the remaining selenium remains unilluminated. The object of the walls or

page_text: plates v¹, which shut-off the boxes of the transmitting and receiving devices A
and A¹ as regards the object or as regards the eye or the photographic camera and
which leave free only a small slit for the passage in and out of the rays that are to
be or have been, transmitted, is to protect particular parts of the apparatus from other
rays injurious to its proper operation.
Method and Apparatus for Reproducing Pictures and the like at
a Distance by Means of Electricity.
We, JAN SZCZEPANIK, Engineer, and LUDWIG KLEINBERG, Banker, both of I Barten-
steinstrasse 16, Vienna, Austria, do hereby declare the nature of this invention and
in what manner the same is to be performed to be particularly described and
ascertained in and by the following statement:-
This invention relates to a method and an apparatus for transmitting a picture or
representation of an object (hereinafter called the picture) and rendering it visible in
its natural colours at a distant place by electrical means.
According to this method the picture that is to be rendered visible at a distance
is broken up into a number of points and the several rays corresponding to these
points are combined together again to form a picture by means of two pairs of
mirrors placed at the transmitting and receiving stations and oscillating synchronously;
for the purpose of transmission, the differences of light of the rays of light passing
from the picture-points obtained by breaking up being first converted into differences
of current, and the latter being then transmitted through the line conductor to the
receiving station and there re-converted into differences of light.
The conversion of the light rays into electrical current impulses can be effected in
various known ways. If the conversion of the several points of the picture that is to
be rendered visible take place in sufficiently rapid succession, the eye of the observer
will receive the impression of the entire picture, and if the picture be reproduced
repeatedly in sufficiently rapid succession, the observer will receive the impression of
a permanent picture, the subject of which may appear to be at rest or in motion
according to the nature of the successive pictures thus "telelectroscoped."
A suitable arrangement of apparatus for carrying out this method comprises
therefore two main portions-viz. the transmitting device and the receiving device
which are connected together by conducting wires or, it may be, by a single wire
only.
In each of the two devices there are arranged two oscillating mirrors which are
moved synchronously by means of electro magnets. As in transmitting the picture
by means of a single conducting wire only one point of the picture situated at the
transmitting-station can be sent at a time, therefore the mirrors must be so arranged
that in any position and at any instant they will reflect only one of the picture-points
and thus bring each time a ray of definite property or quality into operation in that
portion of the apparatus which converts the differences of light into differences
of electric current.
This portion of the apparatus may be variously constructed according as the
conversion is effected by (a) the variation of the conductivity in consequence of
exposure to light (by using selenium, sulphur, tellurium, soot or lampblack or
other substance having this property); (b) photoelectricity; (c) thermo-electricity;

page_text: (d) radiophonic action; (e) variation of magnetism by exposure to light; or by
other causes.
The rays, which are converted into electric currents of various strengths according
to the colour of the light emitted from the several picture-points, produce at the
receiving-station a corresponding energizing of an electromagnet and the consequent
movement of a prism in such a manner that only a ray of similar kind of the light
falling from a source of light on to the prisin and becoming decomposed thereby, can
reach the synchronously oscillating mirrors at the receiving station. The reflecting
action of these mirrors is such as to cause the picture-point transmitted to the eye of
the observer to be visible to him at the place and in the colour corresponding to the
point at the transmitting station.
We shall now proceed to describe a particular form of construction of this apparatus,
in which a selenium cell is employed.
Fig. 1 of the drawings filed with our Provisional Specification illustrates the
general arrangement of the apparatus (transmitting station and receiving station);
Fig. 2 shows one of the oscillating mirrors;
Fig. 3 shows the electro-magnet for moving the mirror ;
Figs. 4 and 5 illustrate, in plan and in vertical section respectively, the selenium
cell employed; and
Figs. 6 to 9 inclusive are diagrams showing different ways of breaking up the
picture that is to be telegraphed.
Each of the four mirrors a a a¹ a¹ is made by coating the reflecting surface
of the mirror with an opaque mass, and by making, by means of a pointed or
sharp-edged tool (needle) or knife), a straight scratch or cut, so as to produce a
reflecting surface in the form of a very narrow linear strip. By means of a mirror
of this kind, only one line of the object G under observation is rendered visible,
because if the eye is stationary only those rays can reach the eye which are
reflected at an angle that is equal to the angle of incidence at which the rays
projected from a line of the picture in the same plane, fall upon the mirror.
The mirror is fixed to an iron plate b which forms the armature of an electro
magnet E and is provided with pivots c.
By means of the attraction of the armature b in consequence of the action of
the electro magnet E, the mirror a is caused to vibrate, or oscillate and consequently
continually changing lines of the picture under observation become visible, because
the angle of the incident rays and therefore also of the reflected rays is continually
being changed thereby.
Now, for the purpose of breaking up those lines into points, the other mirror a¹ of
the transmitting apparatus A, which is likewise operated by an electro-magnet E¹, is
arranged on the armature b' in such a manner that the reflecting lines of the two
mirrors are situated in planes at right angles to each other. Then in a given
mutual position of the two mirrors, only a determined point of the reflecting line of
the first mirror will appear in the second mirror, and therefore only the reflected ray
corresponding to this point will be reflected by the second mirror.
When the two mirrors vibrate on their pivots c the double reflection causes
rays of different points of the object to fall successively upon a determined part
of a wall w provided in the transmitting apparatus A, and in this manner an endless
line can be formed of the successive points of the picture.
Figs. 6, 7 and 8 illustrate diagrammatically different ways of breaking up the
picture into points k, which follow one another so as to form an endless line K.
The abscissaex of the points k determine the motion of the first mirror, which
oscillates about a horizontal axis, and the ordinates y of the said points determine
the alteration of position of the second mirror, which oscillates about a vertical
axis.
The results of the motion of these two mirrors are the endless lines K, of which
the one shown in Fig. 8 is the longest, because the difference between the move-
ments of the two mirrors is greatest. The greater or less closeness of the succession
>

page_text: of the points in the line K is dependent on this said difference, which therefore
also serves to determine the accuracy of the reproduction of the decomposed picture.
By this means, during the motion of the mirrors, continually changing rays of
light emitted from the picture, are thrown on to a definite spot on the wall w, which
rays differ from one another as regards intensity and also colour.
These differences of light have now to be converted into differences of current, in
order to ensure their reproduction at a distant place.
This is, in the example of apparatus shown, advantageously effected with the aid
of a selenium cell S the conductivity of which, as is well known, is considerably
increased by exposure to light, and is also varied in different degrees by the action of
rays of different colours. This selenium cell is arranged behind an aperture o
provided at the place in the wall w where the ray falls that is reflected from the
second mirror at of the transmitting apparatus. The cell S is included together with
a battery B in a circuit L, which leads to the receiving apparatus A¹, and is there
connected to an electromagnet E' and also to a small incandescence-lamp 1, which is
located on a branch connected to a switch actuated by the armature 62 of the electro-
magnet E2.
When the selenium cell S is not exposed to light, no current passes in the circuit L
because selenium has a very great resistance in the dark. But as soon as a reflected
ray of light falls through the aperture o upon the selenium, this resistance becomes
at once diminished to such an extent that a current flows from the battery through
the circuit, energizing the electro-inagnet E² and rendering the filament of the lampl
incandescent. As the action of the several rays varies according to their colour,
various degrees of conductivity of the selenium are produced, and consequently
battery-currents of various strengths are sent into the circuit L.
For the purpose of converting the differences of current thus produced, back again
into differences of light, there is arranged on the armature 62 of the electro-magnet E²
a prism p, and in the wall w¹ there is provided an aperture of such that of the light
emitted from the incandescent lamp and decomposed by the prism there can pass
through the aperture only the portion that corresponds in colour to the ray to which
the selenium cell of the transmitting apparatus is exposed at the same moment and
which produces a current of a definite strength corresponding to its colour and thus
brings about a corresponding movement of the arinature towards the energized
electro-magnet and consequently a change of position of the prism p.
Instead of the light of the incandescence-lamp l, direct sunlight may be employed,
which will then enter through a slit 02 in the casing and be decomposed by the
prism.
The ray passing through the aperture o¹ of the receiving apparatus-for instance,
a blue ray when the selenium cell is exposed to a blue ray-undergoes, in the same
manner but in the opposite direction, a double reflection by means of two
mirrors a¹a which also oscillate on their pivots c under the action of electro-
magnets E¹ E, and thereby effect the composition of the several successive rays so as
to form a picture or image G¹.
For this purpose all that is necessary is that the mirrors of the two
apparatus A and A¹ move in perfect synchronism. With this object the two electro-
nagnets E E of the mirrors that oscillate about horizontal axes are connected with a
battery B by means of a lead L', whilst the electromagnets E¹ E¹ of the mirrors
that oscillate about vertical axes are connected with a battery B³ by means of a
lead L2; and in each of these battery-circuits there is arranged a current-
interrupting device, an induction-apparatus, a microphone, or some other
device M¹ or M² by means of which the current is constantly interrupted or varied in
strength.
As the light emitted from the object G into the transmitting apparatus A, acts
only at one point in consequence of the operation and position of the mirrors, the
use of an objective may be dispensed with.
In front of the receiving apparatus A¹ there may be arranged a photographic plate

page_text: upon which the object situated in front of the transmitting apparatus will appear
after a certain time, or the eye itself may be employed as a photographic camera, in
which case the several light rays are rendered visible upon the retina. The impressions
of images upon the same are, however, of very short duration and disappear
after 01 to 0.5 of a second. Consequently if the whole of the points of the original
picture be telelectroscoped, the observer will, from this succession of photographs
produced in the eye, have the consciousness of seeing the entire picture just as if the
whole of the points of the picture were transmitted simultaneously.
If, before the complete disappearance of the picture a second, third and so on
repetition of the picture be transmitted in the same way, the eye will receive the
impression of a permanent picture. If the successively transmitted pictures corre-
spond to different phases of motion of the object, the impression of a moving picture
can be made on the retina of the eye; exactly as in the case of the stroboscope,
kinematograph, and the like.
The employment of an objective is of advantage if a large picture is to be trans-
mitted, or if it is to be projected or observed directly to a large scale.
As will be seen, in the apparatus described three batteries B, B1, and B2 and three
conductors 1, 1, and L2 are necessary in order to render its operation possible, the
conductor L, with its battery B, serving for transmitting the picture, and the
electromagnet conductors L1 and L2, with their batteries, serving for moving
the mirrors synchronously.
For great distances between the transmitting and receiving places, it is, however,
desirable, on account of the great cost of a plurality of conductors, to do away with
two of them, so that the seeing from a distance and the synchronous movement of
the mirrors can be effected with a single wire.
This is, as regards the one electromagnet conductor, effected by connecting two
corresponding ones of the electro magnets with the conductor L that serves for
transmitting the differences of light converted into electric currents.
The two other electro magnets cannot, however, be directly connected with the
main conductor, as otherwise the two mirrors of the transmitting or the receiving
apparatus would execute a uniform movement, which would have as a result that there
would always be reflected only a single limited line K in the direction of the diagonal
(as shown in Fig. 9) and there would consequently be transmitted only this line and
not the entire picture. Therefore with the line-conductor L there are connected two
like apparatus (inductors, transformers) and into the secondary conductors thereof
there are inserted the two electro magnets acting on the mirrors; thereby the
number of the current-oscillations is changed uniformly and the electromagnets of
each part A and A¹ of the apparatus will produce oscillations differing in number but
proceeding synchronously in the two apparatus.
When employing three conductors, the electromagnets E E¹ can be used as
microphones acting independently of one another as soon as they are suitably
connected with telephones, the mechanical action on the microphones that takes
place in the case of the ordinary telephone-apparatus, being, of course, omitted.
The signal-bell may be put into circuit in a manner similar to that of the latter
apparatus and the entire apparatus be accordingly used simultaneously for seeing
from a distance and for speaking from a distance. If one or both of the electro-
magnet-conductors be omitted, the microphone will be omitted in one or both of the
parts of the apparatus (transmitting or receiving station).
To ensure certainty in the operation of the arrangement for a long time, it is
essential to remove the drawback attaching to the hitherto known selenium-cells
serving for different purposes and consisting in that with constant illumination the
selenium loses in sensitiveness to light.
This is attained by using the construction of selenium cell shown in Figs. 4 and 5.
This consists of two concentric brass-rings between which there is put, as a
lining, a thin annular layers of selenium, so that a disc is produced; this can be
displaced in slow rotation about its axis t by means of a clockwork t' (Fig. 1).
On

page_text: the brass-rings rest two contact-makers u u¹, which are connected with the battery B
or with the line-conductor I. The disc is placed in a part of the apparatus shut off
from the interior by the wall w, so that during its rotation only a small portion of the
selenium ring s can be struck by the ray passing in through the opening o, whilst
the remaining selenium remains unilluminated. The object of the walls or
plates v¹, which shut-off the boxes of the transmitting and receiving devices A and A¹
as regards the object or as regards the eye or the photographic camera and which
leave free only a small slit for the passage in and out of the rays that are to be or
have been transmitted, is to protect particular parts of the apparatus from other rays
injurious to its proper operation.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed, we declare that what we
claim is:-
1. The herein described method of electrical transmission of a picture or
representation of an object for the purpose of rendering the same visible in its natural
colours at a distant place according to which by means of two oscillating mirrors at
the transmitting station, the picture or representation to be transmitted is split up
into a number of points constituting an endless line, the differences of light of the
rays emitted from the picture points at the transmitting station are converted into
differences of current, and the said differences of current are transinitted through an
electric circuit to the receiving station, and are there converted back again into
differences of light which are re-composed to form the picture or representation by
means of two mirrors which vibrate synchronously with the mirrors of the transmitting
station.
2. In carrying out the method referred to in Claim 1, effecting the conversion of the
light differences into current differences by causing the rays reflected at the
transmitting station to act upon a selenium cell S which sends into the circuit I.
currents corresponding to the variations in the conductivity of the selenium cell
produced by the action of the light upon it.
3. For carrying out the method referred to in Claim 1, apparatus comprising a
transmitting station A having two linear mirrors a a¹, vibrating in planes at right
angles to each other, and a selenium cell S, upon which the light rays emitted from
the several picture points are thrown in succession by the double reflection of the
mirrors and their movement by electromagnets E E¹, and a receiving station A¹
comprising a prism p illuminated from any suitable source, and two mirrors a a¹
which vibrate synchronously with the mirrors of the transmitting station, and which
receive light rays by means of the movement of the prism p produced by the
electromagnet E2 that is energized on the exposure to light of the selenium cell, said
light rays being of the same colour as the corresponding rays emitted from the object,
and being composed by means of the double reflection so as to form a picture or
image.
4. In apparatus such as referred to in Claim 3, for the purpose of seeing at a
distance with the use of only one conducting wire, the connection of two of the
electromagnets E E E E¹ which serve to produce the synchronous motion of the
mirrors a a a¹ a¹ directly to the line conductor L, and the inclusion of the other two
electromagnets in the secondary circuits of two inducting devices or transformers which
are connected to the line circuit.
5. In apparatus of the kind referred to in Claim 3, the combination of the
electromagnets E E¹ arranged in separate leads L1 L2, with auditory telephones,
so that the apparatus can be utilized at the same time for seeing at a distance
and speaking at a distance.
6. In apparatus such as referred to in Claim 3, constructing the selenium cell S in the
form of a selenium ring 8 arranged between two concentric brass rings r, r¹ the disc
so formed being revolved slowly behind an aperture o which allows the light rays
emitted from the object to pass through after being reflected, so that only a smali
portion of the selenium is exposed to the light at one time..

page_text: 7. The apparatus for seeing distant objects by electrical means shewn in and
described with reference to the drawings.
Dated this 16th day of November 1897.
F. WISE HOWORTH,
46, Lincoln's Inn Fields, London, W.C., Agent for the Applicants.