23 of the bus bars 20 the clamping feet 36 can be snapped into place in the device or connector adapter 30 in this case a spring loaded locking element 37 can project into at least one bus bar receptacle 31 besides the contact element 32 as shown in fig2 2 a and 3 the locking element 37 is placed behind the transition from the end section 23 to the section 22 of the bus bar 20 and assures that the device or connector adapter 30 is maintained on the mounting unit 10 even if no lock or locking means 51 such as for example the connecting device or connecting means 50 are provided for securing on the platform 11 or the bus bar holders 8 if a locking means for securing on the platform 11 is provided the additional locking element 37 can be omitted as shown in fig1 flat bus bars can also be used as the left side of fig1 and 2 and the enlarged partial view in accordance with fig2 a show following the plug in movement the plug elements 15 and 17 of the connecting elements 14 and 16 are introduced into the connecting element 40 at the device or connector adapter.