"光电式开关掣" can be translated as "photoelectric switch" or "photoelectric switch actuator" in English.
Here, "photoelectric" refers to the technology or principle that involves the interaction of light and electricity, while "switch" denotes a device for making and breaking the connection in an electric circuit. The term "actuator" can be added if you want to emphasize the mechanical part that operates the switch, though in many contexts, "photoelectric switch" alone is sufficient.