IMPROVEMENTS IN TELEPHONES
Year: 1878

page_text: LETTERS PATENT to William Henry Preece, of Wimbledon, in the County of
Surrey, Civil Engineer, for the Invention of "IMPROVEMENTS IN TELEPHONES."
PROVISIONAL SPECIFICATION left by the said William Henry Preece at
the Office of the Commissioners of Patents on the 1st June 1878.
WILLIAM HENRY PREECE, of Wimbledon, in the County of Surrey, Civil
Engineer. "IMPROVEMENTS IN TELEPHONES."
This Invention relates to improvements in telephones, especially those employed
for the reproduction of musical sounds.
An electric telephone is as is well known an instrument which causes matter at a
distance to vibrate in unison with other matter vibrating at homo. The latter, by
its motion or vibration, is made to form or to vary electric currents.in such a way
as to act electro-magnetically, electrostatically, or electrolytically on the former,
and to reproduce in it similar sonorous vibrations.
In Riess's, Gray's, Varley's, Bell's, and other known forms of telephone, these
sonorous vibrations are reproduced directly by the action of the electricity, and are
reinforced by simple sounding boards or resonators. Now according to this In-
vention, the vibrations produced in the receiving instrument are transferred from
their source to fixed or stretched membranes or diaphragms in such a way as to
increase the amplitude of vibrations, and the quantity of air thrown into sonorous
vibration.
Any approved kind of transmitter is applicable to this form of telephone, but I
propose to use that known as Hughes', using several of his sounding tubes joined
in series or in quantity according to the resistance to be overcome.
The receiving instrument will consist of a polarized relay, whose armature,
vibrating in unison with the original source of sound, will, by its connection
through a wire with the diaphragm of a drum similar to that of the toy telephone,
reproduce the transmitted sounds.

page_text: In order to increase the sound I propose to extend the free end of the armature
beyond the relay, so as to give that end an amount of motion greatly in excess of
that requisite for making and breaking contact; and by connecting the diaphragm
with this free end by means of a wire I am enabled to multiply the amplitude of
the vibrations.
SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said William Henry Preece in the Great Seal Patent Office on the 30th
November 1878.
WILLIAM HENRY PREECE, of Wimbledon, in the County of Surrey, Civil Engineer.
"IMPROVEMENTS IN TELEPHONES."
This Invention relates to improvements in telephones, especially those employed
for the reproduction of musical sounds.
An electric telephone is, as is well known, an instrument which causes matter at
a distance to vibrate in unison with other matter vibrating at home. The latter,
by its motion or vibration, is made to form or to vary electric currents in such a
way as to act electro-magnetically on the former, and reproduce in it similar
Bonorous vibrations.
In Riess's, Gray's, Varley's, Bell's, and other known forms of telephone, these
sonorous vibrations are reproduced directly by the action of the electricity, and are
reinforced by simple sounding boards or resonators. Now according to this In-
vention the vibrations produced in the receiving instrument are transferred from
their source to fixed or stretched membranes or discs in such a way as to increase
the quantity of air thrown into sonorous vibration.
Any approved kind of transmitter is applicable to this form of telephone, but I
propose in general to use the instrument known as Hughes' microphone.
The receiving instrument will consist of a polarized relay, whose armature,
vibrating in unison with the original source of sound, will, by its connection
through a wire with a drum head similar to that of the toy telephone, reproduce the
transmitted sounds, whether articulate or otherwise.
In the accompanying Drawing, Fig. 1 shews in partial sectional elevation the
arrangement of apparatus which I employ for transmitting musical and other
sounds, drawn to the full size.
A represents the ordinary Hughes' microphone, connected by means of insulated
wires a, a, with the reel on the polarized relay B, a battery C being placed in the
circuit. The relay consists of a horse-shoe magnet b, to one pole of which one end
of an elastic steel armature b¹ is attached by a clamping screw, the other end being
free to vibrate in front of the other pole of the magnet. Around this pole is the
coil b2 of insulated wire, which forms part of the electric circuit. When a sound
is delivered into the microphone the pivotted tube a¹, or its equivalent, which forms

page_text: the electric connection between the wires a through the carbon block a', will be
thrown into vibration, and the even flow of the electric current being thereby
disturbed, the elastic armature b' of the relay will be caused to vibrate in unison,
as is well understood, thereby reproducing at a distance the sound received into
the microphone A. In order to increase the volume of the sound produced in the
relay the vibrating armature 61 is connected with a sound amplifier D by means of
a wire d. This sound amplifier may consist of a piece of animal or vegetable
parchment d', stretched over a conical tube d³, and secured in place by a hoop d³,
similar to a drum head; or it may consist of a disc or plate of ebonite or of thin
sheet iron, secured in a frame or open case. The wire d will be attached to the
centre of the disc plate or parchment in any convenient manner that will ensure the
transmission through the wire of the vibrations of the armature b¹ to the disc plate
or membrane.
It will now be understood that any sounds delivered into the transmitting
instrument A will be reproduced in the receiving instrument B, and the volume
of this received sound will be increased by the sound amplifier D; the increase of
the volume of the sound will vary according to the size of the disc or membrane
put into vibration.
I find by experience that in transmitting sounds to one person a disc of about
two inches in diameter will produce a good result, but I propose to increase the
area of vibration relatively to the increased volume of souud required to be
produced to suit various sizes of auditorium.
I also propose to connect with a vibrating armature two or more sound amplifiers
of the proportion above indicated, so that the sounds transmitted from the Hughes'
or other instrument may be heard simultaneously by two or more persons.
Fig. 2 illustrates this modification, where three sound amplifiers D, D, D, are
shewn as connected by wires or threads d, d, d, to the elastic vibrator b¹.
I may remark that in place of the Hughes' microphone the combined instruments
B and D), as shewn at Fig. 1, may be used for transmitting articulate and other
sounds to a polarized relay fitted with a sound amplifier, as above explained; thus
the same instruments may be used indifferently as sound transmitters and sound
receivers.
Having now set forth the nature of my Invention of " 'Improvements in
Telephones," and having explained the manner of carrying the same into effect, I
wish it to be understood that under the above in part recited Letters Patent I
claim, connecting to the vibrating armatures of sound receiving instruments, sound
amplifiers D, in the manner and for the purpose above set forth.
In witness whereof, I, the said William Henry Preece, have hereunto set my
hand and seal, the Twenty-ninth day of November, in the year of our Lord
One thousand eight hundred and seventy-eight