A mobile device includes a trigger having a rod-like body fixed at one end. A housing has a first hole into which the body is inserted. A sensor detects that the trigger has been operated in the direction in which the body is pulled from the hole. A buzzer is activated in response to the sensor's having detected the operation of the trigger. A second hole is formed in a firmly fitted member. The body is inserted in the second hole so as to be freely slid forward or backward against the hole. The fitted member is fitted firmly in the entrance portion of the first hole; and a sealing member contacts the internal wall of the first hole and the body.