红绿灯电路Red-yellow-green LED circuit

用单刀双掷开关控制红绿灯。压向两边时分别为红灯、绿灯亮，不压任何一边时黄灯亮。 A Single-Pole Double-Throw switch for controlling red-yellow-green lights. When hitting one side, the red (or green) light is on. When neither of the poles is connected, the yellow light is on.