to one another respectively the plug 24 with the circumferential wall 25 is thus in cross section substantially rectangular the circumferential wall 25 surrounds the contact pins 15 that are positioned at a spacing to one another and are connected electrically conductingly with electric or electronic components arranged within the assembly housing 3 the diameter of the contact pins 15 is selected such that it is minimally smaller than the diameter of the insertion bore 14 of the insulation bodies 11 in the frame part 2 when the plug 24 is inserted into the plug receptacle 8 between the circumferential surface of the contact pins 15 and the inner surface of the insertion bores 14 there is a flame proof or spark ignition proof gap 33 that is defined by din en 50018 and din en 60079 on spaced apart parallel sidewalls 26 27 of the assembly housing 3 there is a locking pin 28 respectively these locking pins 28 are positioned opposite one another and project in opposite directions and outwardly moreover on the exterior sides of the sidewalls 26 27 a stay 29 is provided respectively and the stays 29 are positioned opposite one another the wall section 30 of the sidewalls 26 27 is somewhat inwardly recessed and delimited by.