A vandal resistant light signal unit consisting of a modular integrated circuit arrangement having an insulative circuit board, which has a first broad area layer of conductive material on one side of the circuit board and a second broad area layer on an opposite side of the circuit board. The first...http://www.google.com.au/patents/US5909182?utm_source=gb-gplus-sharePatent US5909182 - Vandal resistant light signal unit
