IMPROVEMENTS IN ACOUSTIC TELEGRAPHS
Year: 1876

page_text: PROVISIONAL SPECIFICATION left by Thomas Alva Edison at the Office of
the Commissioners of Patents on the 26th July 1876.
THOMAS ALVA EDISON, of Menlo Park, in the State of New Jersey, United States
of America. “IMPROVEMENTS IN ACOUSTIC TELEGRAPHS."
It is well known that if two bars or forks of steel of equal length, breadth, and
thickness be secured at one end and properly adjusted they will vibrate at the
same rate of speed. Reeds of this kind have been used in telegraphs.
I have availed of this well-known operation to construct a peculiar telegraph
that is capable of being used either singly, one instrument at cach end, or two or
more instruments at each end of different tones or pitch, so that the instrument at
one end energises the instrument at the other end of corresponding pitch.
The Invention consists of two acoustic reeds, tuning forks, or other bodies
following the law of the pendulum, operated directly by electro-magnetism or
indirectly by the intervention of sonorous bodies or columns of air between such
reeds, tuning forks, or other bodies following the law of the pendulum and the
electro-magnet; such electro-magnetic acoustical reeds are placed at the two ends
of a telegraphic circuit, and being provided with contact breaker points, switches,
connections, and other proper devices, vibrate when properly adjusted in perfect or
practically perfect unison with each other.
The Invention further consists in combining with such acoustical instrument
of other contact devices besides those that are necessary to operate the reeds
themselves, which contact devices serve to throw the wire upon which the electro-
magnets operating such reeds are placed upon a new set of clectro-magnets entirely
disconnected from the reed magnets at both ends of the wire simultaneously at
that particular period of time when the wire is not transmitting an acoustical
wave. The second set of electro-magnets contained in a branch circuit at both
ends may be common Morse relays operating sounders and controlled by a key,
the two receiving the same number of waves as the reed but not at the same time,
and occurring with great rapidity act upon the relay in the same manner as a
constant current..
The Invention further consists in peculiar contact points to ensure a perfect
transfer of the wave from the signalling instruments to the reed instruments, and
vice versti.

page_text: The Invention further consists in peculiar forms of reeds and electro-magnets
operating the same to suit the various conditions which arise upon long, short, and
inferior telegraphic circuits.
The Invention further consists in the method of compensating for the mutilation
of the acoustical and signalling waves by the static current, and by derived currents
from contiguous wires.
The Invention further consists in the method of transferring the main wire from
the acoustic magnets and circuit at terminals and at way stations to the signalling
magnets at the same station.
The Invention further consists in the method of transferring the signals from one
circuit into another.
The Invention further consists in the method of transferring the signals into
branch wires.
The Invention further consists in the method of duplexing and quadruplexing
the signalling circuit obtained by acoustical transfer.
The Invention further consists in the method of transmitting two messages in
the same direction upon the circuit obtained by acoustical transfer.
The Invention further consists in the method of signalling (upon the circuit
obtained by acoustical transfer) by the use of polarized relays and reversed
currents.
The Invention further consists in the method of transferring several separate
circuits from into two branches, each by means of local reeds operated by contact
points upon the main line reed.
The Invention further consists in transferring a single circuit to several branches
simultaneously at both ends of the wire, so as to allow the transmission of several
distinct messages in either direction at the same time.
The Invention further consists in the method of regulating telegraphic machinery
so as to run synchronously at both ends of the line in connection with the trans-
mission of telegrams over the same wire at the same time.
The Invention further consists in the method of transmitting messages upon the
acoustic transfer branch as well as the other branch by a reversal of the current.
The Invention further consists in placing upon one telegraphic wire acoustical
relay instruments which serve to work the local acoustical instruments upon
another and distinct wire, the latter of which is divided by such local reed into a
great number of signalling circuits.
In carrying out the means for accomplishing these objects I avail of the tuned
reeds or forks of bell metal, steel, or other metal as the means for producing
synchronous vibrations, and employ electro-magnets for keeping such reeds or forks
in continuous vibration, such electro-magnets being placed in a telegraphic circuit
and contact devices upon the reeds serving to open and close the circuit of such
telegraphic line, thereby keeping both fork or reeds vibrating in the same time.
These reeds or forks are provided with extra contact devices for opening and
closing a local circuit, in which are placed one or more electrically actuated forks
either making the same number of vibrations as the main line forks or the
multiple of the saune, and these local forks move synchronously at both ends of
the line. Connected to these forks are contact points and springs arranged with
several split circuits in which are placed signalling instruments. The connections
being the same at both ends of the line, and these forks and their contact points
and springs at each terminal is connected together by another telegraphic line.
The synchronously moving local reeds serving to transfer such telegraph line from
one set of signalling instruments at each end to several other sets of instruments
one after the other with great rapidity, but in such a manner that the main line
is never upon more than two sets of signalling instruments at the same time, hence
several messages may be transmitted over the one wire practically at the same
time. There may be included within the samo local circuit another set of acoustical
transfer forks which may serve to transfer another telegraph line alternately to
several sets of signalling instruments simultaneously at both ends of the line.

page_text: Each one of the branches or splits so obtained and upon which signalling takes
place may be arranged with a Wheatstone bridge, equating resistance condenser,
or electro-magnet, the last two for balancing the static charge of the line so as to
allow of the transmission of two messages in opposite directions at the same time
upon each split; with this arrangement I make use of circuit preserving keys.
In practice I prefer to use polarized receiving relay circuit preserving and reversing
finger keys for signalling.