ILLUMINATION MONITORING CONTROL SYSTEM AND SETTING UNIT USED FOR THE SYSTEM

摘要

PROBLEM TO BE SOLVED: To maintain an easy-to-see display condition by easily restraining a change in contrast of a liquid crystal display panel of a setting unit even if source voltage is in a fluctuating condition in the constitution to generate the source voltage on the basis of a transmission signal transmitted on a two- wire transmission line to which a large number of terminals are connected. SOLUTION: A setting unit 6 connected to a two-wire transmission line 5 has a control part 41 to variably control a contrast value of a display driving part 49 according to a value of source voltage detected so that contrast of a liquid crystal display panel 48 becomes constant by detecting a value of the source voltage. The contrast of the liquid crystal display panel 48 is maintained constant without using a constant voltage circuit by variably controlling a contrast value of the display driving part 49 according to the value of the source voltage.