pantograph

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun An instrument for copying a plane figure to a desired scale, consisting of styluses for tracing and copying mounted on four jointed rods in the form of a parallelogram with extended sides.
• noun A similarly jointed framework, such as a power-collecting trolley on an electric locomotive or an extensible telephone arm.

from The Century Dictionary.

• noun A device made of pairs of perforated arms joined together and used for reducing the cross-head motion of an engine for the purpose of indicating; a reducing motion used in taking indicator-cards of engines and working on the reducing principle of the ordinary pantograph.
• noun An instrument for the mechanical copying of engravings, diagrams, plans, etc., either upon the same scale or upon a reduced or an enlarged scale.

from the GNU version of the Collaborative International Dictionary of English.

• noun An instrument for copying plans, maps, and other drawings, on the same, or on a reduced or an enlarged, scale.
• noun An electrical conducting device consisting of a collapsible frame resembling a pantograph{1}, connected to the top of an electrically-powered vehicle such as a trolley, and used to conduct electrical current between the vehicle and an overhead electric wire, which supplies the power to the vehicle. The variable height of the pantograph ensures that it can move to follow variations in the height of the overhead wires, and thus make constant contact with the wires.
• noun a kind of pantograph for drawing a copy which is inclined with respect to the original figure; -- also called plagiograph.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A mechanical linkage based on parallelograms causing two objects to move in parallel; notably as a drawing aid.
• noun A pattern printed on a document to reduce the ease of photocopying.
• noun rail transport A similarly-formed conductive device, now usually Z-shaped, that collects electric current from overhead lines for trains and trams.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun mechanical device used to copy a figure or plan on a different scale