A converter has a casing and a plug. The casing has a mounting recess, an engaging tab and multiple mounting protrusions. The mounting recess is formed in the casing. The engaging tab is formed on and protrudes from the mounting recess. The mounting protrusions are formed on the mounting recess. The plug is detachably mounted on the casing and has an escutcheon, an engaging protrusion, multiple terminals and a pinhole. The escutcheon covers the mounting recess. The engaging protrusion is formed on the escutcheon, is mounted in the mounting recess and has an engaging hole and multiple holding grooves. The engaging hole is formed in the engaging protrusion to engage the engaging tab. The holding grooves are formed on the engaging protrusion and engage the mounting protrusions. The terminals are formed on the escutcheon. The pinhole is formed through the escutcheon and communicates with the engaging hole.