Improvements in Telephones.
Year: 1892

page_text: Date of Application, 19th May, 1892
Complete Specification Left, 20th Dec., 1892-Accepted, 28th Jan., 1893
PROVISIONAL SPECIFICATION.
Improvements in Telephones.
Sir CHARLES STEWART FORBES Baronet 28 Queens Gate Terrace
London S.W. East India Agent do hereby declare the nature of this invention to
be as follows:
In a former Specification No. 3423 February 22nd 1892 I have described a form
of telephone consisting of two tympans mounted up upon opposite sides of a wide
metal ring so that each tympan may be oppositely polarized by the polar extensions
carrying the inducing bobbins which are adjustably mounted upon the horse shoe,
bar or compound magnet or magnets employed; an ear tube or tubes being inserted
in the ring so as to collect the sound waves from each tympan. I have since found
that I obtain very powerful acoustic effects by mounting the tympans very near to
each other in a narrow ring or chamber the extensions being regulated by special
devices hereinafter described. In carrying my improvements into effect I employ
a narrow ring or box formed of metal, ebonite, or other suitable material about half
an inch more or less in width as may best suit the conditions required. In a recess
formed on opposite sides of the ring are mounted the two tympans, which are
secured by screwed rings. Provision is made for fitting one or more than one ear
tube or trumpet communicating with the interior of the ring which is also provided
with a plate or like means for securing it to the magnet or magnets of straight ;
horse shoe or any other required form. Soft iron extensions preferably of square
shape and screwed, but rounded at the end nearest the tympans upon which the
inducing bobbins are mounted pass through corresponding holes in the ends of the
magnets, or in the pole pieces fitted thereto; these extensions are adjusted by a
milled uut turning in a slot formed in each pole piece or the ends of the magnet; or
each extension is tapped; and adjusted by a screw having a bevelled head covered
by a plate fastened to the outside of each pole piece or magnet end. I sometimes
find it advantageous to mount the inducing bobbins in a recess or hole bored in
each pole piece or magnet end, the extensions which in this case may be either
square or round; pass through the centre of the enclosed inducing bobbin and are
adjusted by two screwed washers or equivalent means. The instrument now
described may be used alone or with a microphone of any suitable form.
Dated May 19th 1892.
.
FRANCIS M. ROGERS,
Agent.
COMPLETE SPECIFICATION.
Improvements in Telephones.
I, Sir CHARLES STEWART FORBES, Baronet, 28 Queen's Gate Terrace,
London, S.W. East India Agent, do hereby declare the nature of this invention
and in what manner the same is to be perforined to be particularly described and
ascertained in and by the following statement:-
My invention consists of two tympans mounted up upon opposite sides of a metal
ring, so that each tympan may be oppositely polarized by the polar extensions
carrying the inducing bobbins which are adjustably mounted upon the horse-shoe
bar or compound magnet or magnets employed. An ear tube or tubes being
inserted in the ring so as to collect the sound waves from each tympan. I have
found that I obtain very powerful acoustic effects by mounting the tympans very
near to each other in a narrow ring or chamber, the extensions being regulated by
Price 8dl

page_text: '8'
Fig. 3 shews a modification of my invention fitted with a trumpet mouthpiece.
Fig. 4 is a side elevational view shewing alternative method of adjusting polar
extensions.
Fig. 5 is a vertical section shewing the inducing bobbin mounted within the pole
piece.
In the drawings 1, is the brass, metal or other ring, 2, are the tympans which are
held in position by the two screwed rings 3. 4, are the polar extensions which may
be of either round or square section and carry upon their inner ends the inducing
bobbins 5, wound with suitably sized insulated wire 5ª, connecting line and earth.
In order to ensure accurate adjustment of the polar extensions 4, they are carefully
fitted into a hole formed in each of the soft iron pole pieces 6, secured to the steel
magnet bars 6ª, by screws 7. The outer end of each extension is drilled and
tapped and a conical headed screw 8, inserted, the inner part of the head of
this screw is made sufficiently wide to cover the hole in the pole piece through
which the extension passes, and an iron cap 9, is fastened over it by screws as
shewn. To prevent either extension turning round, a pin 10 is screwed into it
which engages with a slot 11, in the hole. The ring 1, is secured to the pole pieces
by a plate 12, fastened thereto by means of screws 13.
Upon either side of the ring 1, are two lugs 14, these are cored out so as to form
an elongated opening 15, between the tympans and are bored and screwed at their
outer ends so as to receive the nozzles 16, in which are mounted the flexible ear
tubes 17, carrying the trumpets 18, whereby the sound waves are collected from
between the tympans 2, and conveyed to the ear, or they may be used to transmit
speech when the instrument is used as a simple telephone. The instrument now
described can either be mounted upon a plain wood or other base, or it may be
mounted up in a box fitted with an induction coil, in which case one end of the
wire 5, surrounding the bobbins 5, is coupled to one end of the secondary wire of
the coil, and the line; the other end being connected to earth. The primary wire
being connected by suitable switching gear with a battery and microphone in the
manner well understood.
Although I have shewn a set of independent magnet bars 6º, united by a soft
iron pole piece 6, I sometimes employ a single steel bar, as shewn in Fig. 5. In
such case I find that I obtain a greatly enhanced effect by placing the inducing

page_text: bobbin 5, in a recess or chamber within the substance of the bar, the ends of the
wires 5, surrounding the bobbin are passed through small holes 19, drilled on either
side of the recess or chamber and connected up in the usual manner.
The polar
extensions are by preference made of square section and are screwed and fitted with
wrought iron, or brass washers 20. I have found particularly good effect to be
produced by using an iron washer on the side furthest from tympans and a brass
washer upon the nearest side. To prevent the bobbin 5, from turning round, a
small key of ebonite or metal 21, is fitted into a groove 22, sunk in the hole in
which the bobbin is mounted, a flat or recess being filled in the edge of the ebonite
or other spool or bobbin. By mounting the inducing coil and extensions in the
manner described, the lines of force are more perfectly concentrated, which results
in greatly enhanced speaking effects. The adjustment of the square shaped polar
extensions is effected by turning the washers in either direction which has the effect
of advancing or withdrawing the extension to or from the tympans. In Fig. 4, I
have shewn another method of adjusting the extensions, a slot 23 is cut in the top
of the pole piece or the magnet end as the case may be, and a square hole formed
through which the extension 4, passes, a screw is cut upon the outer part of the
extension which engages with a thread tapped in the milled iron washer 20, the
inner part of the extension is turned and the bobbin 5, forced on. By turning
the milled washer, the extension can be advanced or withdrawn as may be desired
and the correct adjustment with regard to the tympans made. Fig. 3, shews an
arrangement I employ for obtaining very loud acoustic effects from a telephone
constructed in the manner I have described. In this case I dispense with the ear
tubes and at any convenient part of the ring I form a lug 14, cored out as described
and communicating with the space between the tympans. In this lug, I mount a
screwed nozzle 16, which carries a cone 24 of large dimensions preferably made of
card or paper.
I find that when an instrument such as I have described is fitted
with a cone as shewn, the sounds emitted by the vibrations of the tympans are
amplified to such an extent that speech can be distinctly transmitted and received
at some distance from the instrument.
The ends of the extension pieces 4, nearest the tympans may if desired be rounded
as shewn to the right in Fig. 1. The tympan box, tympans and adjustable exten-
sions may with advantage be combined with micro-telephone instruments having
compound magnets arranged so that one and the same magnet or set of magnets
operates both telephone and magneto bell as described in the Specification of Letters
Patent granted to me and numbered 18,423, 1891.
I am aware that the use of double tympans has been described, and I do not
broadly claim such except where combined and arranged in the way and manner I
have shewn, nor do I broadly claim the use of an inducing coil embedded in the
material of the magnet except in the way and manner set forth.
Having now particularly described and ascertained the nature of my said inven--
tion and in what manner the same is to be performed, I declare that what I
claim is :-
1. In a telephone combination the use and employment of two tympans secured
and mounted in the manner described so as to be oppositely polarized by external
extensions adjustably mounted in the horse-shoe or other permanent magnet or pole
pieces connecting together several such magnets, the sound waves being transmitted
or collected between the tympans by the means and in the manner set forth.
2. In a telephone combination having two tympans constructed as described, the
extensions 4, carrying inducing bobbins 5, and having locking pin 10, travelling in
slot 11, in magnet 6", or magnet pole 6. The conical headed screw engaging with
said extension, and the plate 9, screwed to the pole piece or magnet for the purpose.
of adjusting the extensions with regard to the tympans as described.
3. In a telephone combination constructed as described in Claims 1, and 2, the-
combination and use of the tubes 17, and trumpets 18, connected by means of the.

page_text: nozzle 16, with the space 15 between the tympans for the purpose of transmitting
and receiving speech.
4. In a telephone combination constructed with two tympans secured and
supported as described, the use and employment of inducing coils 5, surrounded
by the metal of the maguet 6, or pole piece 6. The rectangular shaped exten-
sions 4, threaded and engaging thereby with the metallic washers 20, which adjust
the same in the way and manner described under Fig. 5.
5. In a telephone combination constructed as described under Fig. 5, the
particular manner of locking the bobbin 5, by means of the key 21, and leading
out the conductors through the holes 19.
6. In a telephone combination having two tympans, the particular method of
adjusting the polar extensions by means of the screwed milled washer 20, mounted
in groove 23, iu magnet 6ª, or polar extensions 6, which engages with the thread
upon said extension.
7. In a telephone combination having two tympans secured as described and
co-operating with polar extensions mounted upon a magnet or magnets or polar
extensions thereon and carrying inducing coils which connect the line and earth,
the use and employment of the lug 14, carrying nozzle 16 and trumpet 24, whereby
speech is transmitted and received from between the tympans 2, as set forth.
Dated December 20th 1892.
FRANCIS M. ROGERS,
Agent.