PURPOSE: To ensure a jack cover to be properly mounted on a casing without degrading the appearance of the casing by engaging the edge section of a pin jack support member with the groove of a jack cover fixing section, and mounting the cover on the rear side a front panel.

CONSTITUTION: When a jack cover fixing section 18 is inserted through a slit formed in a front panel 2, a hook 26 comes to be engaged with the rear side bottom wall 2c of the panel 2, thereby temporarily fastening a jack cover 11. Thereafter, the edge section 34c of one of side walls of a pin jack support member secured to a boss 42 on the panel 2 with a screw 48, comes to be engaged with the groove 25 of the fixing section 18, thereby fixing the cover 11 to the panel 2. By providing the cover 11 at the rear side of the panel 2 via the pin jack support member as mentioned, degradation in the appearance of a casing can be avoided. In addition, the strength of mounting the cover 11 on the panel 2 can be increased by causing the engagement of the edge section 34c of the pin jack support member with the groove 25.