An elecctrochromic system utilizes the benefit both from the continuous variability in transmission and memory in EC devices to provide a partial level of light transmission that is variable while minimizing energy usage. An electrochromic element that is responsive to a momentary application of a signal...http://www.google.com.au/patents/US5384578?utm_source=gb-gplus-sharePatent US5384578 - Electrochromic device capable of prolonged coloration
