| 摘要 |
PURPOSE: To prevent the operation from being interrupted due to disconnection of a light source to execute a stable and positive lighting by providing a switching circuit for lighting-up a normally switched-off light source when a normally switched-on light source is disconnected. CONSTITUTION: When a switched-on light source 1 is disconnected, current flowing in the first light source circuit 3 becomes zero, which is detected by a current detector 30 to be compared to a reference voltage value set by a reference power source 32 in a comparator 31. After it is confirmed that volume control is not zero, a disconnection signal is outputted to a memory 6 and a switching device 5. The disconnection signal is stored in the memory 6, a warning lamp 7 lights, and a warning of disconnection is given to an operator. At this time, the switching device 5 switches the supply of power from a power source 9, from the first light source circuit 3 to the second light source circuit 4. As a result, the normally switched-off light source 2 lights, and a stable lighting is thus continuously executed. |
