Shelf assembly in electronic switching system

A shelf assembly in an electronic switching system in which storability of a cable and coolability of the assembly are enhanced. The shelf assembly comprises an upper stationary rail firmly secured to an upper member of the shelf, an upper slide rail slidably mounted on the upper stationary rail, a lower stationary rail firmly secured to a bottom member of the shelf, and a slide rail slidably mounted on the lower stationary rail. The shelf assembly further comprises a cable box firmly secured to the upper and lower slide rails, the cable box having a plate spreading vertically, an area for receiving the cable being defined in one side surface of the vertical plate; and a drawer unit removably inserted in the cable box along the other side surface of the vertical plate, the drawer unit having a plurality of per-line packages which are withdrawably inserted in the drawer unit, the per-line packages each storing the contents of service per subscriber. A common unit is withdrawably inserted in the shelf, and a cable for electrically connecting the common unit to the drawer unit extends so far as to a front end of the vertical plate of the cable box along the one side surface of the vertical plate.