Still, a clear yes/no answer to whether employees washed their hands well enough could be valuable, both as a preventive tool and a feedback system to improve employee practices.

These elements form a closed feedback system.

Song and drink and passion create a closed feedback system, in which each grows with the others' increase.

Haptic technology (the sensory feedback system between machine and user) should make the experiences more than just visual and aural.

Vessel occlusion tends to be a positive feedback system; an occluded vessel creates eddies in the normally laminar flow or plug flow blood currents.