ABOD: parallelogram
OCE: straight line
O: immobile
OE/OC = BE/BD = k = constant
Figures traced by pointer E and pin C are similar.
Scale factor is k.
This is the case when red tool is immobile (not installed in place of pin C) and the orange pantograph is connected to system of two sliders (by pin C and a hole of the green plate).
A rack-pinion drive turns orange cylinder installed on the blue lower slider. Pitch diameter of the pinion and diameter of the cylinder are equal.
The tool traces red figure (having same size with the figure traced by pin C) on cylindrical surface of the cylinder.
Meshing place of the rack-pinion drive (at upper or lower portion of the pinion) affects direction of the figure traced on the cylinder.