parallel drum การใช้

• In 1923 the original parallel drum was replaced by a bi-cylindro drum which made the winding of coal much easier.
• By the 1880s, lens front mounted accessory shutter boxes were available, containing a rubberized silk cloth curtain ( also called a blind ) with one or more width slit cutouts wound around two parallel drums and using springs to pull a slit from one drum to the other.