Electronic transformers with a self-excited half bridge can be destroyed by high-voltage pulses from the mains supply lead. The display panel includes a first substrate on which pixel electrodes are formed, a second substrate on which a common electrode are formed, and a photo-sensor formed on the first substrate. Specifically, the treatment chamber has an elongate housing through which a formulation flows longitudinally from an inlet port to a first outlet port and a second outlet port thereof. The engaging section connects to the resisting section and includes an engaging wall, the engaging wall defines a notch and forms an extending wall.