This unit is made up of three independent attenuators. They can be used individually or in series to provide any combination of attenuation. Each dial is used to set the attenuation of one of the attenuators. The first dial selects an attenuation from 0 to 50 dB in 10 dB increments, The second dial selects 0 to 10 dB in 1dB increments and the last dial selects 0dB, and 3.0dB to 4.0 dB in 0.1dB increments.