Abstract: The present invention relates to an arrangement for system cameras of the kind which have interchangeable component parts which may be attached to a camera body, said component parts communicating electrically with each other and with the camera body. Into this system has been incorporated a data bus which extends partly into the camera body and partly into the other interchangeable parts via contact devices arranged on the connections between the various parts. The different parts of the system are able to communicate with each other and individual component parts can be allocated new functions via the small number of conductors in the data bus circuit without having to alter the contact configuration between the component parts.