This document is the Owner's Manual for the Yamaha PS-20 and PS-10 portable keyboards. It covers assembly instructions, including how to install the battery pack and AC power adapter (IPP-1). The manual explains that the battery pack and AC adapter have the same shape and can be quickly interchanged.
The guide also details the features of the PS-Series, which can now be used as a power amplifier. It includes sections on auxiliary terminals, optional accessories, and precautions for use.