The Analog Alignment Diskette (AAD) is a precision 
measurement tool for adjusting mechanisms and recording heads 
in flexible disc drives. The AAD is particularly suited for the 
initial alignment of new drives and drive realignment after 
replacement of major components. It requires an oscilloscope, 
access to drive circuitry test points and a user with some 
servicing experience.

The Dysan Digital Diagnostic Diskette (DDD) is a reference 
disc for evaluating a drive's overall alignment and performance.