Manufacturers description

A15AS In-line Switchable Attenuator
Use the A15AS balanced-line attenuator to prevent low-impedance microphones (rated at 150 or 600 ohms) and high-output condenser microphones from overloading low impedance inputs in high sound pressure level applications. The values of attenuation can be switch selected for 15, 20, or 25 dB.
Use with any low-impedance microphone, including phantom-powered condenser microphones, such as the Shure SM81. It can be used in line between the microphone and its power supply. (This model is not suitable for use with the condenser powering system called "A-B Powering.")
The A15AS attenuator bridges the microphone output and allows maximum signal handling with a minimum of loading-caused distortion or reduction in clipping level.
Specifications
Frequency Response
Flat, 20 to 20,000 Hz +- 0.5 dB
Impedance
Input (XLR Female): 1,000 ohms
Output (XLR Male): 150 ohms
Attenuation (switch selectable)
15 dB, 20 dB, or 25 dB
Case
Full magnetic shield; steel with gray enamel finish
Dimensions
19 mm (3/4 in.) diameter; 114 mm (4 1/2 in.) long
Note: The equivalent single series simplex-powering resistance is 215 ohms; this resistance should be considered in addition to any existing circuit resistance when using the attenuator.
Description
SHURE PROBLEM SOLVERS
Filters, attenuators, transformers, switches and impedance adapters to solve interface problems in installlations and in the field.