1) used in e.s.r, the attenuation of the microwave power passing along a waveguide is achieved by means of a metal plate placed along the axis of the waveguide. The degree of attenuation increases as the plate is moved away from the wall of the waveguide toward the center. In IR and UV spectroscopy, the attenuator is a toothed comb, grid, or star arrangement introduced into one beam of a spectrometer, operated either automatically through an electronic servosystem, or manually to balance the radiation in both beams.