A moveable headrest is mounted on or with respect to a support for supporting a user in viewing images in a standing, seated, or reclining posture. The ink is substantially the same color as the imaging element background and remains substantially hidden until the imaging element background changes color when heated. A response of the target system to a manifestation of the periodic modulating signal in the command signal is detected, and a feedback signal is produced from the detected response. Also provided are packaged products comprising a package and a plurality of dispersible absorbent products or articles.