Abstract: In a ring communications system including a plurality of line concentrators that are connected in the form of a ring, the line concentrators are connected together via a main ring, and the terminal stations connected to the line concentrators are connected to the main ring via ring subsidiaries. The main ring and the ring subsidiaries are connected together via ring connection switches that so work as to connect or disconnect the main ring and the ring subsidiaries. The ring connection switch is so constructed as to maintain the connected condition even when the power source of the line concentrator is in the turned-off state.

Abstract: A station diagnosis method in a communications network system including a closed ring transmission line and a plurality of data stations which can be connected to the ring transmission line by a plurality of line concentrators disposed in the ring transmission line wherein an internal ring transmission line is formed in the line concentrators so that the operation states of the line concentrators are diagnosed by transmitting diagnosis data through the internal ring transmission line.

Abstract: A visible image magnetic card employing a magnetic recording sheet having a sandwich of a magnetic recording layer and a base sheet. A display sheet has a transparent display area with a display cell is formed between the display sheet and the magnetic recording sheet. The cell houses a mixture of magnetic particles and a transparent or translucent fine fluidizing powder.

Abstract: This invention relates to a loop transmission system which has a plurality of stations connected to a loop transmission path to transmit data among the stations. In the transmission frame to be sent out from the sending station, specific information is included for identifying each frame and this information is held in the sending station. When the transmission frame returns to the sending station after being transmitted through the loop transmission path, the specific information in the frame is received and compared with the information held in the station and, if they coincide, it is decided that the transmission frame has been correctly received by the intended receiving station.

Abstract: A loop transmission system including a plurality of stations connected in series in a looped transmission line to transfer data among the stations, wherein the stations include a supervising station and at least one terminal station and the transmission line is duplicated so that when a fault occurs in currently used one of the transmission lines, the other transmission line which has been used as a spare is used for transmission of data, while the supervising station sends out a specific signal to the spare transmission line and the terminal stations each determines one of the transmission lines through which the specific signal is detected, as the spare.