The shutter is wound by rotating a knob on the front of the shutter which tensions a coiled spring. As the spring is wound a plate attached at its centre rotates, to one end of the plate is a connecting rod that runs to the piston of the delay cylinder. Also attached to the piston is a rod that connects to the shutter blade. The rotation of the spring pushes the connecting rod into and out of the cylinder (setting the shutter takes the piston and shutter blade through a complete cycle). When the shutter is released the spring unwinds causing the blade to lift and then descend. A valve at the top of the cylinder regulates the escape of air and so the exposure. Motion of the blade is roughly uniform throughout the exposure. The Improved model differs in setting the speed by a pointer against a scale. The Original had the speeds shown on a cap at the top of the cylinder. The shutter was made in several sizes the smallest had speeds to 1/100, larger models had speeds up to 1/50 or 1/32.