In a storage system having a plurality of control units each connected with a plurality of disk units, it is provided that a replication is created in the volume of the disk units connected to different control units. During a conversion step where the connections of a given capacitor may be varied, the switches to the given capacitor are both placed in a high impedance state during a decision period of a comparator. An LED light source serving as an array of discrete light source is constituted by a red emission LED, a green emission LED, a blue emission LED, and another green emission LED provide alternately and discretely along the light entrance surface. A SIM card is mounted between the cover and the insert.