The Test Station, AN/USM-646 is a controlled diagnostic test instrument that utilizes Analog Signature Analysis (ASA) to
isolate malfunctions in electronic modules. A sinewave stimulus is used to display the current versus voltage characteristic of an
unpowered component on a CRT. The current/voltage characteristic is called an analog signature. The AN/USM-646 is software
driven and is capable of storing the analog signature. This enables the technician to learn and save the signatures of a good module
and utilize the stored signature to fault isolate defective modules.