A COMMUTATOR FOR DOUBLE TRANSMISSION AND REVERSION OF CURRENT WITH CONTACT TO EARTH FOR SUB- MARINE TELEGRAPHY
Year: 1878

page_text: PROVISIONAL SPECIFICATION left by Edgar Edmonds at the Office of the
Commissioners of Patents on the 18th October 1878. (Communicated from
abroad by M. le Comte Emilio Siccardi, of Turin, Italy.)
EDGAR EDMONDS, of the Firm of Robertson, Brooman, and Company, of 160,
Fleet Street, in the City of London, Patent Agents. "A COMMUTATOR FOR DOUBLE
TRANSMISSION AND REVERSION OF CURRENT WITH CONTACT TO EARTH FOR SUB-
MARINE TELEGRAPHY." (Communicated from abroad by M. le Comte Emilio Siccardi,
of Turin, Italy.)
The inventor of the finger key for submarine transmissions (described and
specified in the Patent No. 275 of the 21st of January, 1878) has thought it
expedient to give a new arrangement to those keys by which the contacts for line
currents and for discharge currents may be obtained alternately either by the inter-
position of a contact between the line and earth, between the line current and the
discharge current, or by causing the line current to pass without interrupting the
contact between the line and earth.
The following is an arrangement devised for this purpose:-A metallic piece is
in permanent contact with a bridge piece. Two platinum screws establish constant
contact with the copper of the line; nothing more is changed of the arrangements
explained in the preceding description before mentioned.
It is easily understood that when one or the other of the two keys is lowered by
means of their two articulated extremities contact is immediately established between
the line or earth and the copper pole of line, but directly one or the other of the
two articulated pieces abandons this contact one or the other of the two keys
presses on the metallic piece above referred to, which being in direct communication
with the bridge piece thus establishes during the time the key is pressed down a
contact between the line and earth.
As soon as the finger is released from the key the latter in rising causes a zinc
discharge current on the line by means of two extremities, which extremities being
articulated in a direction contrary to that of the other two extremities before
referred to only act when the keys return to their original position, whereas on the

page_text: contrary the two last-named extremities only act by the lowering of the keys, as
already described in the preceding description.
It will be seen that by this arrangement instead of passing the discharge current
on the line immediately after the line current a contact between the line and earth
is interposed between the two, which in certain cases is preferable.
The same result may be obtained with the keys reduced to two articulated
extremities in the following manner :-
The metallic piece here continues to establish contact between the line or earth
and the copper of the line, the two platinum screws will establish contact with the
zinc pole of the discharge; that is to say, in this arrangement nothing is changed
of the arrangement previously explained, but the following parts are added:-
The two keys carry fixed at their front ends two ratchets of tempered steel, and
placed in front of these ratchets are two teeth, also of steel, which are fixed on two
elastic or springy blades, the whole being screwed on to the apparatus stand itself.
The two teeth communicate directly and solely with the bridge piece herein-before
referred to.
Thus when one key is lowered it first encounters one of the teeth, that is to say,
the bridge piece instantly leaves this and presses on the metallic piece, that is to
say, with the copper contact of the line. Scarcely has the key left this latter when
by its return movement it again encounters the tooth, and leaving this immediately
sends the zinc discharge current along the line.
It is therefore seen that with this last arrangement is obtained not only a contact
between the line and earth, interposing itself between the line current and the
discharge current, but also the means of causing the line current to pass without
interrupting the contact between the line and earth, which can but greatly augment
the rapidity of transmission.
If it is desired to obtain longer contacts a mercurial system of contact may be
substituted for the fixed rods, nothing more being changed for this last arrangement.
This Invention is not limited to the special arrangements and to the mechanical
combination described and shown, but it extends to all other analogous mechanical
arrangements, which by a simple lowering and rising of two lever keys, without
clock work, wheelwork, or other complicated means, permits of alternately obtaining
the contacts for line currents and for those of discharge however by interposing
between these a contact between the line and earth, or by causing the line current
to pass without interrupting the contact between the line and earth.