2131 for receiving the key button 11 referring to fig2 4 and 5 in assembly the capturing element 13 is assembled into the assembling groove 21 of the housing 20 the main body 131 is received within the corresponding retaining slot 2135 and the first elastic arm 135 and the second elastic arm 137 are received within the assembling groove 21 the distal fixing end 1351 is secured to the fixing post 2111 the fixing post 2111 passes through the fixing hole 1353 of the first elastic arm 135 after that the key button 11 is assembled into the accommodating groove 2131 and is latched to the capturing element 13 the two latching hooks 113 and the stopping post 115 of the key button 11 respectively pass through the corresponding two assembling holes 1311 and the accommodating hole 1315 of the main body 131 of the capturing element 13 the circuit board 40 is mounted on the housing 20 with the switch 30 aligning with and accommodated within the resisting groove 1313 of the capturing element 13 referring to fig4 6 in use when pressing the key button 11 the capturing element 13 is pushed by the key button 11 against the.