| 摘要 |
PURPOSE:To judge whether a switching element is in an ON or an OFF state from ON-OFF state of a light emitting element by a method wherein the light emitting element, which emits light by a control current, is connected to a control terminal through which the switching control current is made to flow. CONSTITUTION:When the output control signal of a control circuit 4 is at a zero level, no base current flows through a transistor 1, so that the transistor 1 is put in an OFF state, in result as no current flows through a light emitting diode 2, consequently the light emitting diode 2 emits no light. When the output control signal of the control circuit 4 is at a high level, a base current flows through the transistor 1 through the intermediary of the light emitting diode 2, and the transistor 1 is turned 'ON'. At this point, as a base current flows through the light emitting diode 2, the diode 2 emits light. As mentioned above, the light emitting diode 2 emits light when the transistor 1 is ON and no light when the transistor 1 is OFF, so that it can be recognized by viewing the emission of the light emitting diode 2 whether the transistor 1 is in an ON or an OFF state. |
