Optical filters carefully transfer light in a specific range of wavelengths or colors while obstructing what remains. These dyed plastic or glass devices are placed in the optical path. They are described by their frequency response, and this identifies how the scale and stage of each frequency component

This device integrates all of the senses used for learning. It is one of the basic instruments used for visual-motor training, and helps with direction, rhythm, eye-hand coordination, and work and shape recognition. It consists of an aluminum case with illuminated membrane switches organized along a