System for interchangeable attachment of electrical equipment

A system for interchangeable mounting of electrical equipment, comprising a mounting plate having a front and rear surface and bounding an aperture extending between said surfaces;

• at least one item of electrical equipment including an electrically insulating frame insertable into said aperture in direction from said front to said rear surface;
• and means for guiding said frame during the insertion thereof and for releasably arresting the same in a fully inserted position thereof, including at least one pair of long and one pair of short walls which are rigid with said mounting plate and extend rearwardly from said rear surface thereof to bound with one another at least one cavity constituting a continuation of said aperture, at least one detent projection rigid with each of said short walls and extending therefrom into said cavity, and at least one pair of elongated grooves on opposite sides of said frame in positions corresponding to those of said detent projections and parallel to said direction of insertion, each of said grooves having a leading guiding portion of a first depth, and a trailing detaining portion of a second depth exceeding said first depth, said short walls being resiliently yieldable to be deflected by said frame upon contact thereof with said detent projections during the insertion so that said detent projections enter said guiding portions of said grooves to guide said frame in said direction of insertion and snap into said detaining portions upon juxtaposition therewith in said fully inserted position to thereby prevent undesired extraction of said frame from said aperture of said mounting plate.