Systems and methods disclosed herein may be useful for manual braking systems for use in, for example, an aircraft. The bi-directional optical link comprises a detector having an upper surface facing a predetermined direction and a beam turning device located over the surface. The primary transceiver unit may send data destined for the subscriber transceiver units through the optical router, and the subscriber transceiver units may send data destined for the primary transceiver unit through the optical router. The first closing unit has a coupling mechanism to couple to a second closing unit which acts on one of the first and second roof parts and which interlocks the acted upon roof part to a third roof part or to a body part. A history record provides a record of a classification of a recently-executed instruction. The low filming and streaking occurs even in the presence of quaternary ammonium biocides.