a housing which has a horizontally-long shape, and has, on a front surface, an opening portion, said front surface having upper and lower peripheral edges which are curved so as to become higher at a center in a horizontal direction and become lower toward the right and left end portions when viewed respectively from upper and lower side surfaces;

a display which is provided at a center portion inside said opening portion of said housing and at a position lower than the upper and lower peripheral edges of said front surface when viewed respectively from the upper and lower side surfaces;

an operating mechanism which includes a keytop provided at a position higher than the upper and lower peripheral edges of said front surface when viewed respectively from the upper and lower side surfaces in a right and left portions inside said opening portion of said housing; and

a separate cover which is attached onto said housing so as to cover said opening portion in a manner such that its upper and lower edges are along the upper and lower peripheral edges of said front surface, wherein

said cover includes

a transparent window formed at a position corresponding to a position of said display, and

an opening which is formed at a position corresponding to a position of said operating mechanism so as to expose said operating mechanism therethrough.