Abstract: The present invention relates to a system for optical transmission of information over a multiplexed logical ring structure comprising a number of nodes, of which at least one is a master node, as stated in the independent claim 1. Said ring structure is a combination of a number of logical optical rings on the same physical fiber ring. Possible embodiments are disclosed in the dependent claims.

Abstract: The invention concerns a contact device that comprises a carrier member (10), a receiving unit (12) for receiving at least one optical fibre (14), a control circuit (16) that includes a converter for converting optical signals to electrical signals and vice versa and a first contact member (18) connected to the control circuit (16) and designed such that a second contact member may be connected to the first contact member (18) for conducting electrical signals from and to the first contact member (18). The receiving unit (12), the control circuit (16) and the first contact member (18) are fixed relative to the carrier member (10). The contact device is designed to be fixable at a structural element (20) in a room (22) or other part (22) of a building. The invention also concerns a use of the contact device.