AUTOMATIC DIMMING DEVICE FOR TUNNEL ILLUMINATION

摘要

PURPOSE:To correctly control the illumination in a tunnel by sequence- controlling an illumination circuit with a compensating circuit in accordance with the time schedule preset in response to the daily illumination change outside the tunnel when a normal output signal is not sent from a light receiver circuit. CONSTITUTION:When a normal output signal is sent from a light receiver circuit 3, an output circuit 5 driving an illumination circuit 1 is controlled by a control circuit 4, and illumination apparatuses in the tunnel are turned on or off in response to the illuminance outside the tunnel. When a normal output signal is not sent from the light receiver circuit 3 for some reason, a compensating circuit 6 sequence-controls the output circuit 5 driving the illumination circuit 1 so that the illumination apparatuses are turned on or off according to the preset time schedule in response to the daily illuminance change outside the tunnel. Even if a detecting means 3 with a light receiving element does not generate the output in response to the illuminance outside the tunnel for some reason, the illumination in the tunnel can be dimmed automatically and correctly.