A toy based on a geared 5 bar linkage consists of a turntable on which you can put a paper disk. Two gears are attached to the turntable and a pair of rods attached to the gears. As you turn the turntable, the smaller gears turn which makes the rods travel. A pen attached to the rods traces out a pattern
You can drag the big circle and watch the pattern be traced. You can also drag one of the gears to alter their relative location.