| 摘要 |
PURPOSE:To facilitate the operation of an acoustic equipment by installing the first and the second transistor and by allowing the second lamp to light with the brightness corresponding to the variable voltage when the variable voltage is over a prescribed value and by allowing the second lamp to light with a constant brightness when the variable voltage is less than a prescribed value. CONSTITUTION:When the slide terminal 2a of a variable resistor 2 is slided to a grounded side from the edge of a power source side, a voltage Bm gradually lowers, and the brightness of a lamp 3 reduces. since the base voltage of the first transistor Q1 lowers, each emitter current of transistors Q1 and Q2 lowers, and also the brightness of the second lamp 5 reduces. When the base voltage of the transistor Q1 becomes below a prescribed value, the transistor Q1 is put into non-conductive state, and at the same time, the emitter potential of the second transistor Q2 lowers, and the transistor Q2 conducts. If, at this time, the emitter current is set to the nearly equal value to the emitter current of the transistor Q1 in the case when the voltage Bm is max., the lamp 5 lights-up with the equal brightness to that in the case when the voltage Bm is max. |
