The recorder, which was shown in operation, naturally stood in the place
of honour, and attracted great attention.
The minor features of the recorder have been simplified by other
inventors of late; for example, magnets of steel have been substituted
for the electro-magnets which influence the swinging coil; and the ink,
instead of being electrified by the mouse-mill, is shed on the paper by
a rapid vibration of the siphon point.
To introduce his apparatus for signalling on long submarine cables, Sir
William Thomson entered into a partnership with Mr. C. F. Varley, who
first applied condensers to sharpen the signals, and Professor Fleeming
Jenkin, of Edinburgh University. In conjunction with the latter, he
also devised an 'automatic curb sender,' or key, for sending messages on
a cable, as the well-known Wheatstone transmitter sends them on a land
line.
In both instruments the signals are sent by means of a perforated ribbon
of paper; but the cable sender was the more complicated, because the
cable signals are formed by both positive and negative currents, and not
merely by a single current, whether positive or negative. Moreover, to
curb the prolongation of the signals due to induction, each signal was
made by two opposite currents in succession--a positive followed by a
negative, or a negative followed by a positive, as the case might be.
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