A compound of Formula, wherein each X is independently fluorine or chlorine; n is 1 or 2; R1 is C3-C8 alkyl, phenyl or benzyl; and R2 is C1-C6 alkyl; and its production and use. The standard element has a first standard plane opposite to a measured object. The engine protection system includes visual and audible signals responsive to the parameters. A trigger device detects relative movement between the bi-stable display panel and the data input device and generates a trigging signal to shift data address in a data shifter, thereby renewing image data in the bi-stable display panel.