Polygraph (duplicating device)

A Polygraph is a duplicating device that produces a copy of a piece of writing simultaneously with the creation of the original, using pens and ink.

Patented by John Isaac Hawkins on May 17, 1803, it was most famously used by the third U.S. president, Thomas Jefferson, who acquired his first polygraph in 1804 and later suggested improvements to Charles Willson Peale, owner of the American rights.

[6] Mechanisms of this type are more generally known as pantographs, which include simple devices for making copies at various enlargements or reductions by tracing over a drawing.

In the portable version the bridge, side posts, and a bottom cross piece form the outer rim of enclosure when in the state for transportation.

The device consists of two pens transmitting motion in five degrees of freedom through four interlinked mechanisms: In addition, a vertical suspension spring balances the weight of the moving parts.

The range of the planar mechanism must be sufficient to encompass the papers (individually) being written upon and allow access for each pen to its respective inkwell.