- Siphon recorder
The siphon recorder is an item of
telecommunications equipment invented byWilliam Thomson, 1st Baron Kelvin in1858 . In many ways, it anticipated the moderninkjet printer though it seldom operated reliably.The principle of the telegraph siphon recorder is exactly the inverse of the
mirror galvanometer . In the latter we have a small magnet suspended in the centre of a large coil of wire—the wire enclosing the magnet, which is free to rotate round its own axis. In the former we have a small coil suspended between the poles of a large magnet—the magnet enclosing the coil, which is also free to rotate round its own axis. When a current passes through this coil, so suspended in the highly magnetic space between the poles of the magnet, the coil itself experiences a mechanical force, causing it to take up a particular position, which varies with the nature of the current, and the siphon which is attached to it faithfully figures its motion on the running paper. The point of the siphon does not touch the paper, to avoid impeding the motion of the coil.The siphon and an ink reservoir are together supported by an
ebonite bracket, separate from the rest of the instrument, and insulated from it. This separation permits the ink to be electrified to a high potential while the body of the instrument, including the paper and metal writing tablet, are grounded, and at low potential. The tendency of a charged body is to move from a place of higher to a place of lower potential, and consequently the ink tends to flow downwards to the writing tablet. The only avenue of escape for it is by the fine glass siphon, and through this it rushes accordingly and discharges itself upon the paper. The natural repulsion between its like-electrified particles causes the shower to issue in spray. As the paper moves over the pulleys a delicate hair line is marked, straight when the siphon is stationary, but curved when the siphon is pulled from side to side by the oscillations of the signal coil.Bibliography
*cite book | title=Degrees Kelvin: A Tale of Genius, Invention and Tragedy | year=2004 | publisher=Washington: Joseph Henry Press | id=ISBN 0-309-09073-3 | author=Lindley, D. , "p."191
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