AN AUTOMATIC COMBINED KEY SWITCH FOR USE IN CON- NECTION WITH SUBMARINE OR OTHER TELEGRAPHIC WIRES
Year: 1875

page_text: PROVISIONAL SPECIFICATION left by William Ladd at the Office
of the Commissioners of Patents, with his Petition, on the 16th
October 1875. A communication from abroad by Andrew Jamieson,
of Pernambuco, in the Empire of Brazil, Telegraphic Engineer.
I, WILLIAM LADD, of Beak Street, in the County of Middlesex,
Philosophical Instrument Maker, do hereby declare the naturo of the
said Invention for "AN AUTOMATIC COMBINED KEY SWITCH FOR USE IN CON-
NECTION WITH SUBMARINE OR OTHER TELEGRAPHIC WIRES," to be as follows:
The object of the Invention is to construct a key switch which will
prevent the telegraph clerks from leaving their switches over for
sending signals when they should be in a position for receiving or "vice
versa," and also to combine on the same base the whole arrangement of
sending key and switch.
The sending key arrangement employed in conjunction with the
present Invention is the same as that in ordinary use, and to this is
applied the automatic switch which comprises the following parts, viz.,
a rocking spindle which passes underneath the sending pedals, and is
provided with adjustable centres for bearings. This rocking shaft

page_text: carries two cam pieces which are situated immediately underneath the
left and right hand keys respectively, and are of such a form and size
that when their shaft is turned on its centres they will be brought into
a position for receiving a signal, and then they effectually lock the keys
from below, thus preventing the operator from sending until his switch
is turned for the same; the cam piece will then make contact with a
spring which is in connection with the terminal, and therefore with
the sending shunt (or lead) and line while both cams clear the keys
depressed.
One corner of the cam piece when turned from a position of sending
to one of receiving clear, the point of the spring thereby leaving the
same perfectly free, while the other corner moves underneath the left-
hand pedal, and as before mentioned locks the same. In the middle of
the rocking spindle is fixed a counterweight which serves as a suitablo
rest for the middle finger when the operator is sending, and on the
removal of his hand (from its weight acted on by gravity) it falls and
turns the spindle with the cam pieces, thus automatically placing the
instrument in a receiving position.
It is to be noticed that a permanent electrical connection exists
between the end terminal of the left-hand sending key and the rocking
spindle through a copper wire led underneath the ebonite base and
brought up in a spiral form through a hole immediately underneath the
counterweight and soldered to the centre of the spindle where it will
have little play, or, if preferred, this electrical connection may be made
by a similar spring bearing always on one of the cam pieces, and
connected by wire to the left-hand terminal. From this it will be seen
that when joined to the recorder the out going currents split between
the resistances of the sending shunt and the instrument coil, whereby
the greater quantity goes direct to line through the former, and the
smaller through the instrument coil (owing to its resistance being the
higher), thereby producing the sending signals, which not only acts as a
detector to show that the circuit is all right, but proves a check on what
may be sent with the corresponding signals read off at the other end of
the cable.