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Equation 5 · The Machine Before Electronics

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AnA_n

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the while. Read the equation part by part below; each part has a contextual explanation and a link to its mathematical background.

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AnA_n

Symbol A_n

the while.

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subscript

subscript

The lower label selects a particular version, component, or indexed member of the quantity. For example, x₀ and xₜ can be values at different positions.

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Thomson’s machine implements exactly that division. Each of the ten shafts in the 1872 instrument carries an overhead crank with a pulley pivoted on a parallel axis that is adjustable for the range applying to that place — the amplitude AnA_n — and each crank can be positioned and clamped to correspond to the required tidal epoch — the phase ϕn\phi_n . The shafts are geared so that their periods are proportional to the periods of the tidal constituents — the frequencies ωn\omega_n [ 3 ] . The summing cord performs the ∑\sum . The pen writes h(t) against a moving paper roll while a single crank drives everything at once.

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