Abstract: ASSA ABLOY Entrance Systems AB has developed the present invention relates to a connection device (100) for a door operator system(S) for opening and closing an opening (O). Said door operator system(S) comprises a door (20) and a drive unit mounted on said door (20) and arranged to move the door (20) between an open and closed position. The door operator system comprises an elongated transmission member (40) extending along a side of the opening (O), wherein a driven transmission member (34) of said drive unit (30) is arranged to interplay with said first elongated transmission member (40) so as to move the door (20) between the closed and open position. Said tension arrangement (100) comprises a bracket member (110) for facilitating attachment of said tension arrangement (100); a tension device (T) comprising a connection member (120) for connecting said first elongated transmission member (40) and a spring arrangement (130) comprising a spring member (132).