Year: 1887

page_text: Date of Application, 8th Sept., 1887.
Specification Accepted, 14th Oct., 1887
[Communicated from abroad by EUGENE EMMONS GRAVES, of Bridgeport, Connecticut,
United States of America, Manufacturer.]
I, HENRY HARRIS LAKE, of the firm of Haseltine, Lake & Co., Patent Agents,
Southampton Buildings, in the County of Middlesex, 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 :-
For the purpose of transmitting signals over a line telegraphically or telephonically
three kinds of electrical currents are recognized, denominated respectively the inter-
mittent, the pulsatory and the undulatory. Intermittent currents are produced by
actually making and breaking the circuit, and in this particular they differ radically
from pulsatory or undulatory currents in producing either of which the circuit is not
interrupted. The pulsatory current is caused by suddenly increasing or suddenly
diminishing the intensity of the existing or normal current. The undulatory current
is caused by gradually increasing and diminishing said intensity from minimum to
maximum and back again.
The distinction between the pulsatory and the undulatory current is fully set out in
the specification of Letters Patent to William Morgan Brown, No. 4765, sealed the
15th May, 1877, and dated the 9th December, 1876. The same distinction is also
graphically illustrated in Fig. 1 of the accompanying drawings. In Fig. 1 the

page_text: currents are direct, that is, the electrical impulses 62 63 6² are all of the same polarity,
either positive or negative. The direct intermittent current is represented in line 1
of Fig. 1.
The impulses 62, 63, etc. are all of positive or all of negative electricity and the
vertical thickness of the lines 622 measured from the zero line, represents the
intensity of the current at the part observed. The horizontal extension of the line z¹ z¹,
indicates the duration of the electrical impulse and the horizontal extension of the
space shows the length of time the current is absent from the circuit.
'
The direct pulsatory current is shown in line 2, Fig. 1. The current of electricity
represented is continuous but it changes suddenly in intensity, the elevations 6' 6' etc.
indicating the impulses of maximum intensity and the depressions etc. the impulses
of minimum intensity. As before the vertical thickness of the line indicates the
strength of the current.
The direct undulatory current is shown in line 3, Fig. 1. As before, the vertical
thickness of the line expresses the strength of the current, the elevations 6 6 express
the impulses of maximum intensity and etc. those of the minimum intensity.
The changes of intensity as illustrated in line 3 do not occur with the suddenness
characteristic of pulsatory currents, as shown in line 2, but have hitherto been assumed
to be proportional to the changes in the density of the air during the production of a
sound.
Referring now to Fig. 2, in line 1 of said figure the graphic representation
of the pulsatory current shown in line 2 of Fig. 1 is reproduced enlarged for
convenience of comparison with another graphic representation of a pulsatory
current shown in line 2 of Fig. 2. In the current represented in line 1 of Fig. 2
the changes in intensity or strength occur with extreme suddenness as indicated
by the perpendicular sides of the elevations 63. If however the changes occurred
less rapidly during one phase of the to and fro vibration it is evident that one
side of the elevations 662, would be graphically represented as inclined. This
condition is shown in line 2 of Fig. 2. Here one phase of the to and fro vibration
which constitutes a pulsation occurs in a longer period of time than the other phase.
In such case the longer phase is represented by the inclined sides s while the shorter
phase is indicated by the perpendicular sides of the elevations bas before. In either
of the cases represented in lines 1 and 2, Fig. 2, the current represented is a true
pulsatory current. It has none of the interruptions of an intermittent current, and
obviously not the wave like form of the undulatory current. It is obvious however
that the form of a pulsatory current may vary, that is to say, a pulsation may reach
its maximum with more or less speed. If it does so absolutely instantaneously, then
as shown in Figure 2, line 1, the graphic representation will show straight sided
elevations; if it does so in a given period of time then one side of the elevation will
be inclined in degree proportionately to that time.
Again in the diagram, line 1 of Fig. 2, it is apparent that in the form of pulsatory
current there shown each pulsation instantly attains a maximum indicated by the
vertical side of the elevation, remains at such maximum for a period represented by
the line y, and then falls to normal, as indicated by line z. On the other hand in the
different form of pulsatory current represented in line 2 of Fig. 2, each pulsation
attains a maximum more slowly as indicated by the inclined line s, does not however
remain at such inaximum but instantly falls to normal as indicated by line 2.
It is exceedingly important to note this possible variation in the form of the
pulsatory current, inasmuch as through such variation it becomes possible to transmit
articulate speech telephonically by means of such a current.
The claim has been advanced by many that it is impracticable to transmit articulate
speech by the aid of a current of electricity unless that current be rendered undulatory
in form; in contradistinction to being rendered either intermittent or pulsatory.
It is claimed that the strength of the current must vary in intensity as the air varies
in density, during the utterance of a sound, and that the undulations caused in the
current must necessarily copy the phases of the air vibrations, or in a word, that

page_text: speech or the quality (timbre) of sound cannot be electrically transmitted save by
means of the undulatory current and by virtue of that particular form of current to
the exclusion of all other forms. It has been expressly affirmed by the advocates of
this theory that the transmission of articulate speech or the quality (timbre) of sound
by means of a pulsatory current as hereinbefore defined and as the same is set forth
in the specification of Morgan Brown aforesaid is a total impossibility.
The present invention rests upon the new principle that articulate sound and the
quality (timbre) of sound can be perfectly transmitted telephonically by the pulsatory
current, and the said invention consists in the method or art of carrying the aforesaid
principle into practical effect. One mode of accomplishing this result is hereinafter
described and illustrated but it is to be understood that the invention is not limited
to the said particular mode nor to any particular mechanisın embodying it, but is to
be taken in the broadest sense as including any and all methods of production of the
result herein set forth through the practical application of the aforesaid principle by
substantially equivalent modes of carrying the same into effect.
Referring now to Fig. 3, let A represent an electro-magnet and B an armature
supported in any way in front of the pole of said magnet. Suppose a current of
electricity to flow through the coil of said magnet. If the armature B be moved by
hand for example to the position B¹ then there will be caused in the magnet coil a
current due to the movement of said armature and dependent upon the rate of travel
thereof. This current being superposed upon the normal battery current may
augment the strength thereof.
Suppose the armature now to be released. Then being free it will be attracted
by the magnet and moved back into position B. But now the energy which causes
the mechanical movement of the armature is exerted by the electro magnet. That
energy is necessarily derived from the current which energizes the magnet. Hence
the current itself is weakened correspondingly to the energy so exerted.
At every vibration of the armature therefore, extraneous energy is applied
mechanically to move it in one direction away from the pole, and the energy of the
current is drawn upon to move it back to its starting point so completing the
vibration.
In the case supposed and illustrated in Fig. 3, the hand of the operator mechanically
moves the armature B away from the pole, the current due to this movement is added
to the normal current; the magnet itself (not the hand of the operator) carries the
armature B back again; the magnet must therefore expend energy; it derives its
energy from the current; therefore the current is weakened. Now clearly the
armature is under direct mechanical control of the operator only when it is being
moved away from the magnet; when it is returning the magnet is merely exerting
its attractive power subject to no variation. Regarding the movement of the
armature B as a vibration it follows that at one phase of the to and fro movement it
is under mechanical control whereby the movement and consequently the current
which it induces in the magnet coil may be varied, and at the other phase of its
movement it is not under a control which is in like manner mechanically varied.
Fig. 4 is introduced for purposes of comparison with Fig. 3 and is a diagram
representing the parts of an ordinary magneto telephone. Cis a diaphragm of induc-
tive material forming the armature of the electro magnet A through the coil of which
a battery current passes. A sound wave in air striking this diaphragm may be
supposed to curve it inward to the position indicated by the dotted lines C and one
half of a to and fro vibration is thus produced. The force which brings the diaphragm
back to its normal position so completing the vibration is obviously its own resiliency.
But this is rendered active by the energy expended in moving the diaphragm inward;
so that in fact a part of the energy of the sound waves which moves the diaphragm
inwardly is stored in the spring which reacts to move the diaphragm outwardly. It
follows therefore that during both phases of its vibration, in and out, the diaphragm
armature is in the direct mechanical grasp, so to speak, of the sound wave which
moves it, as much so substantially as if it were vibrated to and fro by the hand.

page_text: Hence the movement of said armature causes direct and inverse currents in accordance
with its direction of motion, and these direct and inverse currents being caused by
and corresponding to both the condensations and the rarefactions of sound waves
imitate or copy the character of the movement of the air particle in vibrating; and,
because the movement of such a particle may be represented graphically by a sinuous
or undulatory curve so these currents which copy that movement may be similarly
represented. Fig. 4, therefore, represents an apparatus operating by means of an
undulatory current.
Returning now to Fig. 3, the armature B is controllable by the sound waves while
moving away from the magnet as well as it is controllable by hand or any other
mechanical means. Such being the fact it follows that the resulting current in the coil
does not copy the movement of the air particle during both phases of its to and fro
vibration but only during one phase, namely, that one during which its movement
is controlled by the sound wave, and not during the phase when its return is effected
simply by the attractive energy of the magnet.
This is graphically illustrated in Fig. 5, in which variation in duration of current
is measured along the line A B, and variation in strength of current along the
line A C, the point A indicating zero or the starting point. At each vibration (one
rarefaction and one condensation), during the phase of rarefaction the armature is
moved away from the magnet and the strength of the normal current is increased by
the current so induced. This increase of strength is represented by the inclined
line a.
The phase of rarefaction being completed the phase of condensation begins,
but now the magnet simply retracts the armature expending energy and so the
current comes back to its normal condition. This return effect is represented by the
line b. The following wave may be similarly represented by the line a¹ and b¹ and
so on.
By comparing Fig. 5 with line 2 of Fig. 2 the similarity in the graphic represen-
tation of the working of the present apparatus and the graphic representation of the
peculiar form of pulsatory current will be apparent.
Figs. 6, 7 and 8 illustrate diagrammatically an apparatus for effecting the transmis-
sion of articulate speech by means of a pulsatory current produced by the voice.
Fig. 6 shows the apparatus at rest, and Figs. 7 and 8 illustrate the relation of the
parts where the diaphragm controlled by the voice is moving respectively inwardly
and outwardly. In these three figures similar letters of reference indicate like
parts.
E is an electro magnet energized by a constant current, F is an armature supported
upon the elbow lever H which is pivoted at G. I is a diaphragm. J is a point at the
lower end of the vertical arm of said elbow lever which point comes opposite the
center of the diaphragm.
When sound waves are produced, in front of the diaphragm I, that diaphragm in
vibrating moves inward or outward as indicated in Figs. 7 and 8. In moving inward
it meets the point J of the lever H and so carries the armature F away from the pole
of the magnet E. During this movement of the armature its lever is in direct
mechanical connection with the diaphragm I, is controlled by said diaphragm and
hence is controlled by the sound valves which vibrate said diaphragm. Therefore a
current due to the movement of said armature so produced is added to the main
current.
On the return movement of the diaphragm I as indicated in Fig. 8, it moves away
from the point J of the armature lever H. Consequently the armature is left free to
be attracted by the magnet E. Not being in contact with the diaphragm which in
fact is constantly moving away from said contact, the armature is not controlled in
any sense by said diaphragm. Hence the magnet simply expands energy in attracting
said armature and the current yielding said energy at once falls in strength. The
current is therefore rendered pulsatory and not undulatory or intermittent, in form,
and by reason of its being thus rendered pulsatory in form it becomes capable of trans-
mitting the quality of sound and articulate speech.

page_text: Having now fully described and ascertained the nature of the said invention
and in what manner the same is to be performed as communicated to me
by my foreign correspondent I declare that what I claim is :-
1. The method of transmitting vocal or other sounds including articulate speech
which consists in producing pulsations corresponding to said vocal or other sounds in
an electric current traversing a line conductor, substantially as herein before
described.
2. The method of and apparatus for producing pulsations in an electric current
traversing a line conductor corresponding to vocal or other sounds, substantially as
hereinbefore described.
1
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C.,
Agents for the Applicant.