401 the passive member 42 has a main body 420 a pair of fixing arms 421 extending downwardly from the opposite sides of the main body 420 and a projecting portion 422 extending upwardly from the main body 420 between the fixing arms 421 the main body 420 has a hollow 423 surrounded by the fixing arms 421 each fixing arm 421 has a setting hatch 424 connecting with the hollow 423 the passive member 42 is mounted on the locking arms 362 of the locking section 36 and the hollow 423 is placed over the receiving channel 361 rightly the fixing arms 421 matches with the locking arms 362 by the setting hatches 424 clasping corresponding blocks 363 the fixing section 401 of the active member 40 is placed in the receiving channel 361 and the engaging section 402 protrudes out of the hollow 423 to be located at the frontage of the projecting portion 422 at the same time the end of the engaging section 402 collides with the lower surface of the main body 420 normally the switch set 4 is closed when a card is inserted the engaging section 402 is pressed down together with the.