In the bathroom, sensory functions, especially sight, are restricted. In such an environment, products designed for visually impaired users can improve usability for users without visually impairment. With this in mind, a new remote controller of the gas water heater in the bathroom was developed. It included improvements for visually impaired users. In particular, we applied origin signals to the new product and used them to notify a standard value on numerical value setting. To confirm the validity of the improvements, usability testing were executed for the remote controller before and after the improvements and if the results were compared. As a result, it became clear that visually impaired users could operate the controller appropriate voice guidance and origin signals were added. In addition, it was shown that this improvement did not disturb usability and improved usability for a user without visually impairment. The validity and problems on use of the origin signal also became clear.
