An installation switching device has a housing and screw connecting clamp with an essentially frame-shaped clamping part having longitudinal faces, narrow faces and broad faces, a head-clamp screw received in a clamping part threaded aperture, and a current rail arranged fixed in the device extending through the frame-shaped clamping part interior, wherein a current rail broad face is oriented, as assembled, parallel to a clamping part broad face facing the head clamping screw, the screw supporting itself, screwed in, on the current rail, wherein consequently, the clamping part is displaceable in its longitudinal direction, parallel to the narrow face, relative to the current rail by further screwing in the head clamping screw so a connecting conductor can be fixedly clamped between the current rail face remote from the screw and the clamping part broad face remote from the screw, the housing having a screw receiving region guiding the screw head.