Crystal Palace International Electric Exhibition 1881-82
År: 1882
Sider: 102
UDK: 621.30 : 06 (064)
DOI: 10.48563/dtu-0000189
Official Catalogue, Edited by W. Grist with Specially Prepared Plans, showing the position of each exhibitor and indicating the spaces lighted by the various sytems.
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17
[1 6.] SERIES OF COILS AND NEEDLES USED IN
CONNECTION WITH THE NEEDLE SYSTEM
OF COOKE & WHEATSTONE.
b. 1846. The original form, with long coils and permanent
magnetic needles.
c. 1848. Holmes’ small Diamond Needle. This was a great
improvement in the original form, as it increased the speed of
working considerably by diminishing the arc of vibration of the
•p 00(^1
d. 1851. Clark’s Needle.
e. 1866. Varley’s Induced Needle.
N.B.—This prevented demagnetization by atmospheric elec]
taicity—a very frequent source of trouble.
f. 1866. Brittan’s Undemagnetizable Needle.
g. 1869. Spagnoletti’s Induced Needle.
[17.] 1878. NEALE’S ACOUSTIC DIAL, employed on a
single-needle instrument in the place of the ordinary dial. Is
very similar in action to a Siemens’ Relay, but the needle is held
in the vertical position, by a spiral spring behind the dial.
[18.] 1880. TIN PLATE SOUNDER for converting the
single-needle instrument from a visual to an aural apparatus.
The sounder is fixed to the dial of the ordinary instrument, the
ivory pins of which are removed; the needle strikes against the
curved surfaces and produces audible sounds.
[19] . 1855. BRIGHT’S BELL WITH RELAY.
Used by the Bi’itish. and Irish. Magnetic Telegraph. Company
The single-needle alphabet is produced by striking two bells of
different tones, the hammers being actuated by electro-magnets
worked by a relay and local battery. The relay is double-acting,
and consists of two electro-magnetic bobbins placed side by
side, their ends being furnished with pole pieces turning inwards.
Between these pole pieces at each, end of the bobbins, the ends
of permanently magnetized needles, pivoted on vertical axes,
play; these needles are so placed as regards their polarity that a
current in one direction moves the needle which, closes the local
circuit of the right-hand bell, and a current in the opposite
direction, moves the othei’ needle, which, closes the local circuit of
the left-hand bell. The signalling key used with this installment
is similar to that used with Highton's Single Needle. This
instrument superseded Henley's magnetic-electric system.