IMPROVEMENTS IN TELEPHONIC TDATED
Year: 1883

page_text: LETTERS PATENT to Henry Alabaster, of South Croydon, in the County of
Surrey, and Tom Ernest Gatehouse, of Camberwell, in the County of
Surrey, both Electricians for an Invention of IMPROVEMENTS IN TELEPHONIC
TDANGUITTED
PROVISIONAL SPECIFICATION left by the said Henry Alabaster and Tom
Ernest Gatehouse at the Office of the Commissioners of Patents on the
11th January 1883.
HENRY ALABASTER, of South Croydon in the County of Surrey, and Toм
ERNEST GATEHOUSE, of Camberwell, in the County of Surrey, both Electricians,
"IMPROVEMENTS IN TELEPHONIC TRANSMITTERS
"
Our invention relates to the construction of instruments, to receive vocal or
other acoustic impulses, for transmission in a telephonic circuit, technically known
as "transmitters," and is designed to effect louder and clearer transmitted articu-
lation, by means of the said "transmitter;" and, by the absence of a fixed
vibrating diaphragm or tympan, to afford an increased sensitiveness, and to avoid
the Creation of any continued dominant tone, or "buzz," from loud speaking,
during the use of the instrument.
Our invention consists of the combination with one another, of a bridge, with
accurately plane and smooth under surface, resting upon, and forming electrical
contact between, two electrodes, also with accurately plane and smooth upper
surfaces, all preferably of carbon, the said bridge receiving, direct, the acoustic
impulses, through a confined passage, such as a speaking tubo.
The contact surfaces of the said bridge and electrodes, must be carefully worked,
so as to form plane smooth surfaces as far as practicable.
The bridge must be of sufficient thickness and rigidity, to maintain its plane
surface, and remain inflexible in regard to its parts, though agitated as a whole,
by the successive acoustic impulses.
The bridge must be perfectly free and uncontrolled, in contact with the
electrodes; a steady pin or pins being conveniently used, to keep it inplace, and
to prevent it touching the surrounding case.
One of the electrodes has, preferably, a smaller contact area than the other, and
they are, respectively, in electrical contact with the telephonic circuit, in any
known manner.
The said electrodes may be attached to a non-conducting block placed in, or
forming part of, a suitable case.
To the upper part of this box, a speaking tube is attached, so that the acoustic
impulses of the voice may impact directly, upon the upper surface of the bridge.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Henry Alabaster and Tom Ernest Gatehouse in the Great Senl
Patent Office on the 11th July 1883.
HENRY ALABASTER, of South Croydon, in the County of Surrey, and Tox
ERNEST GATEHOUSE, of Camberwell, in the County of Surrey, both Electricians,
"IMPROVEMENTS IN TELEPHONIC TRANSMITTERS"
Our invention relates to the construction of instruments to receive vocal or
ncoustic impulses, for transmission in a telephonic circuit, technically known as
"transmitters," and is designed to effect louder and clearer transmitted articulation,
and in the absence of a fixed vibrating diaphragm or tympan, to afford an increased 1
sensitiveness, and to avoid the creation of any continued dominant tono or “bužz
during the use of the instrument.
"
Our invention consists of a bridge with an accurately plane and smooth under
surface, resting upon and forming electrical contact between electrodes, the said
electrodes also having accurately plane and smooth upper surfaces, all preferably, 1
but not necessarily, of carbon, the said bridge receiving direct the acoustic impulses
through a confined passage, such as a speaking tube, combined therewith.
In order that our invention may be the better understood, we now proceed to
describe the same with reference to the drawings hereunto annexed, in which like
letters refer to like parts throughout the figures.
Figure 1 is a sectional elevation of our device.
Figure 2 is a sectional plan of same through X Y.
Figure 3 is a transverse section through V W.
Two carbon electrodes A, and a guide pin B, are set on an insulating base C, the
electrodes A being connected to brass plates D, on one side of the base, which are
convenient for connection to the circuit E. The bottom surfaces of the electrodes
may be coated with a deposit of metal, conveniently copper, and connected by a
soldered wire to the contact brass plates D. This connection, however, may be
made in any suitable manner.
Upon these electrodes A, rests a carbon bridge F, porfectly free above and
around, sufficiently thick and rigid to be inflexible in itself, but light.enough to be
subject to agitation, under acoustic impulses received through a confined passage
or speaking tube G, as a whole in regard to the said electrodes, which agitation is
electrically conveyed to the circuit E.
The contact surfaces of the bridge F and electrodes A are plane and smooth to
the point of polish, and the bridge is prevented from dancing off the electrodes, or
touching the sides of the casing by the guide pin B, set in the insulating base, and
passing through the centre of the bridge.
The tube G, through which the acoustic impulses are received, is conveniently
fitted to a cap H, of any convenient material, fixed on the casing I; but this cap is 4
not necessarily closed, as it may merely be an open support to the tube; it is only
essential that the acoustic impulses should be made to impinge directly upon the
bridge from the mouth of the confined passage or speaking tube.
The carbon bridge, though shown in the form of a disc, may be a block or of
any other suitable form, and the form of the electrodes may vary accordingly, as 4
may also the form of steady pin or guide.
:
The smooth, plane, contact surfaces of our carbon bridge and electrodes may be
prepared by rubbing the same with uniform pressure upon a plane surfacing block,
which is conveniently of ground glass.
The effective smoothening of the contact faces by this grinding is most essential 5
to the proper action of the transmitter, and must be carried to the point of polish.

page_text: Having now fully described and ascertained the nature and objects of our
invention, and the manner of its performance, be it known that what we consider
novel and useful and desire to protect by Letters Patent is :-
First. in a telephonic transmitter, the combination of a confined passage or
speaking tube, with electrodes supporting a free bridge, inflexible as to its
substance, but subject to agitation as a whole in regard to the electrodes, by
acoustic impulses impinging through the confined passage aforesaid, the contact
surfaces of the bridge and electrodes being plano and smooth to the point of polish,
and the bridge steadied by a suitable guide, substantially as set forth.
Second. In a telephonic transmitter or "tension regulator" the use of electrodes
and free connecting bridge, of which the contact faces aro plane and smooth to the
point of polish, substantially as set forth
In Witness whereof I, the said Tom Ernest Gatehouse, on behalf of myself
and the said Henry Alabaster, have hereunto set my hand and seal this
Eleventh day of July in the year of our Lord One thousand eight hundred
and eighty-three.
Witness :-
JOHN, C. FELL
Fell & Wilding
23 Rood Lane.
London. E.C.
Patent Agent.
TOM ERNEST GATEHOUSE (Ls.)