Abstract: In a network system in which an interconnection is achieved between an LAN terminal connected to an LAN and an ISDN terminal linked with an ISDN via at least an LAN/ISDN inter-working unit coupling the LAN with the ISDN, the ISDN terminal develops a function to multiplex data link connections (communication paths) identified with respective data link connection identifiers (DLCIs) on ISDN channels. After conducting a call establishment to the ISDN terminal, the inter-working unit supplies the LAN terminal with an ISDN channel number and a DLCI designating an ISDN communication path. Thereafter, the LAN terminal sends an LAN frame having an OSI layer 2 header loaded with the communication path information to the inter-working unit. On receiving the LAN frame, the inter-working unit executes a format conversion to convert the LAN frame into an ISDN frame based on the ISDN communication path information.

Abstract: In a program control apparatus with a program ROM which forms sequence control signals for executing various control actions according to specified conditions, a memory circuit is provided which is activated during a particular operation mode to successively store information corresponding to the external conditions and also information on times taken by the operation sequence of the program control apparatus.

Abstract: In a distributed network formed of communication stations having equal control functions, each station which sends a master station (or Active Monitor) determination frame appends a unique identifier to the frame, and each station which receives a frame judges the rationality of the received frame based on the identifier thereby to determine the operation of the self station depending on the result of judgement.

Abstract: A ring network system in which a plurality of line concentrators each having terminal stations connected thereto through respective branch lines are interconnected through at least one ring transmission lines. Each line concentrator includes configuration control switches capable of disconnecting from the ring transmission line all the branch lines placed under control of the line concentrator while holding the ring transmission line in the state to allow communication. The branch line(s) disconnected from the ring transmission line form(s) a local ring through cooperation with an internal transmission line. The line concentrator detected abnormality of communication or the line concentrator to be set to the rest state can undergo internal diagnosis operation or continue to be in the rest state without disturbing the communication among other line concentrators.

Abstract: In a communication system having first and second ring transmission lines for connecting a plurality of stations and for providing opposite signal transmission direction, a first station, which is located just downstream side of a failure point occurred in the first transmission line, sends out a beacon signal along said first transmission line while causing an intentional failure in the second transmission line on its downstream side and a second station, which is located just upstream side of the failure point on the first transmission line, forms a first loop-back path (WRAPA) by detecting the intentional failure on the second transmission line if the second station has received the beacon signal. The first station forms a second loop-back path (WRAPB) by receiving the beacon from the second transmission line which is sent back by the second station.

Abstract: In a communication system having first and second ring transmission lines for connecting a plurality of stations and for providing opposite signal transmission direction, a first station, which is located just downstream side of an failure point occurred in the first transmission line, sends out a beacon signal along said first transmission line while causing an intentional failure in the second transmission line on its downstream side and a second station, which is located just upstream side of the failure point on the first transmission line, forms a first loop-back path (WRAPA) by detecting the intentional failure on the second transmission line if the second station has received the beacon signal. The first station forms a second loop-back path (WRAPB) by receiving the beacon from the second transmission line which is sent back by the second station.

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: In a communication network having a plurality of stations interconnected through a double ring transmission line, a station which detects a failure in the ring transmission line sends out a failure notice data, and a station which has received the failure notice data stops the send-out of its own data and relays the received data. A station which cannot receive the failure notice data loops back and transmission line to form a closed ring transmission line which bypasses a failure location.

Abstract: A local area network communication system in which a repeating installation sets a ring number of a ring from which a communication frame was taken out as a source address of the frame. The repeating installation also sets a ring number of a ring to which a communication frame is to be sent. When a station receives the frame, the station checks the source address of the frame to identify the ring number of the ring to which the source station belongs and checks the destination address to identify the ring number of the ring to which the station itself belongs.