Combined units and image forming system

An image forming system comprising:

• an image forming apparatus having a first side face and configured to form an image on a sheet using a first electric device included in the image forming apparatus;
• a post-processing apparatus having a second side face and including therein a second electric device that performs a predetermined post processing on the sheet on which the image has been formed, the post-processing apparatus being configured to perform the post processing upon being installed beside the image forming apparatus with the second side face closely opposed to the first side face;
• a fixed member disposed on the first side face in a fixed manner;
• a first connector disposed on the first side face in a fixed manner and electrically connected to the first electric device;
• a connecting member disposed on the second side face so as to move in a second direction orthogonal in a horizontal plane to a first direction in which the image forming apparatus and the post-processing apparatus are aligned, and configured so as to be displaced between an engaging position in which the connecting member is engaged with the fixed member and a disengaging position in which the connecting member is disengaged from the fixed member;
• and
• a second connector connectable to the first connector, mounted on the connecting member, and electrically connected to the second electric device,
• wherein the first connector and the second connector are disconnected from each other when the connecting member is set to the disengaging position, and
• the first connector and the second connector are connected to each other when the connecting member is set to the engaging position.