IMPROVEMENTS APPLICABLE TO SUBMARINE TELEGRAPHY
Year: 1879

page_text: PROVISIONAL SPECIFICATION left by Alexander Melville Clark at the Office
of the Commissioners of Patents on the 27th January 1879. A communi-
cation from abroad by François Joseph Fortuni Ailhaud, of Paris, France.
ALEXANDER MELVILLE CLARK, of Chancery Lane, in the County of Middlesex,
Patent Agent. "IMPROVEMENTS APPLICABLE TO SUBMARINE TELEGRAPHY." [A
communication from abroad by François Joseph Fortuni Ailhaud, of Paris, France.]
This Invention relates to novel arrangements in connection with the working of
submarine telegraph cables, which have for their object to return the cable to the
neutral condition, and also to prevent accumulations, and thus permit of the
employment of synchronous instruments, such as the Hughes for example, to which
the system and arrangements hereafter described are more particularly applicable.
Transmission of messages through cables by the Hughes instrument.
Referring to the annexed Drawing, K, L, is a contact finger placed on the front
end of the cam shaft (prolonged about one inch for the purpose), and which during
the rotation of said shaft is caused to rub upon a series of segments insulated from
one another. Two distinct apparatus may be employed at each station, the one for
receiving and the other for transmitting, or one only need be used if a suitable
commutator be employed to change the communications of the segment.
For sending, the contact finger K, L, is in communication with the machine
frame M, and the latter with the cable; the segment B is connected with the
position pole of a battery X; the segment C is insulated; the three segments
D, E, F, are connected with the negative pole of a battery Y.
Three segments G, H, I, are to earth, and the segment upon which the contact
finger lies when at rest is connected with the ingress end of a mirror galvanometer
A, the egress end of which is to earth. Thus when the cam shaft revolves, a
positive current is first sent through the cable and then a negative current, and by
means of a resistance R or a derivation, the strength of the latter current so
regulated that the needle remains almost stationary, which shows that the cable
bas no longer either a positive or negative charge, but has returned to the neutral
condition. A condenser may be employed instead of a battery for compensating.
For receiving, communication with the transmitter is broken, or the communi-
cation with the segments changed by means of the commutator.
The finger
K³, L¹, is connected with the frame M' of the instrument which is in connection with
the cable and with the ingress end of a polarised relay, the egress end of which is
to earth. The segment upon which the finger is when at rest is insulated; segment

page_text: B' is to earth; segments C¹, D¹, are connected to the negative pole of a small
battery Y', which may be regulated by means of a resistance R' or of a derivation.
The segments E, F, are to earth,-and-the-segments-G, H, I, are connected to the
ingress end of a very sensitive mirror-galvanometer A which should not make any
movement when the contact finger has performed a revolution, thus indicating
_that_all_currents have ceased in the cable. The current transmitted_by_the sender
arrives at M¹ and passes thence to relay N, which closes-the-circuit-of-a- local
-battery-P-passing_through_the_Hughes coils V, thus setting the contact finger in
motion; the latter first puts the cable to earth through the segment-B¹, then-in-
passing over segments C¹, D', sends a weak negative current into the cable and
relay N to oppose the positive cnrrent in the cable and return the relay. The
Hughes armature on rising quits the spring T, and the current of the local battery
P ceases to pass through the Hughes coils. Instead of employing a contact finger
and segmental disc, levers and cams may be used. The same result. may also be
obtained by connecting the zero segment with the relay, in this case however the
negative battery current communicating with the segments C', D', is only sent into
the cable, but by means of a lever operated by the rotation of the cam shaft, a
negative current is sent for returning the relay, or this may be done by an
independent mechanical arrangement..