Hitachi, Ltd.

Hitachi Process Computer Engineering, Inc.

Hitachi Cable, Inc.

Sadao Mizokawa

Seiichi Yasumoto

Hisayuki Maruyama

Takuji Hamada

Masahiro Takahashi

Hitoshi Fushimi

Ken Onuki

Masato Satake

Junji Fukuzawa

Toshiyuki Murakami

Toshihiko Uchiyama

Jushi Ide

Hisao Ogawa

Hiroshi Tomizawa

Osamu Anbo

Hiroshi Kuwahara

Eiichi Amada

Yoshitaka Takasaki

Matsuaki Terada

Masakazu Okada

Naoya Kobayashi

Akira Watanabe

Hiroshi Mabuchi

Masanori Kogawa

Toshio Ishihara

Sigeru Fukasawa

Yoshiji Ito

Hiroshi Kaita

Yasuo Hosoda

Hiroaki Ohnishi

Naomasa Hanano

Tadaaki Okada

A plurality of different fault locating functions are provided in a communication system comprising a plurality of terminals connected to a data transmission channel. The functions are at different levels, respectively, ranging from a level for rapid fault location to a level for reliable and sure fault location. Upon detection of an occurrence of a fault, one fault locating function is performed. If the fault is not located accurately located, another fault locating function of a level for more reliable is performed, thus the functions are performed sequentially in the order from the level for rapid location to the level for more deliberate and reliable location. Preferably, the channel is reconfigured to avoid the fault, according to the fault located by the functions of the respective levels. With this arrangement, a fault which does most possibly occur can be located quickly, while another fault difficult to locate can be located accurately.

Method of locating fault of communication system

A data transmission method and system of a token passing type capable of periodically transmitting cyclic data produced in a station to other stations while enabling a packet data communication with high efficiency and without disturbing the periodicity of the cyclic communication. A token circulation time is set to be shorter than a cycle time for production of the cyclic data where no packet data to be transmitted. Also each station will pass an acquired token immediately to the next station if the station has no data to be transmitted. Thus, at least one station can have a token at least two times during the cycle time to transmit the cyclic data and the packet data. Upper limits may be set to capacities of the cyclic data and the packet data which are capable of being transmitted each time the token is acquired.

Data transmission method and system thereof

A data transmission method and system of a token passing type capable of periodically transmitting cyclic data produced in a station to other stations while enabling a packet data communication with high efficiency and without disturbing the periodicity of the cyclic communication. A token circulation time is set to be shorter than a cycle time for production of the cyclic data where no packet data is to be transmitted. Also each station will pass an acquired token immediately to the next station if the station has no data to be transmitted. Thus, at least one station can receives a token at least two times during the cycle time to transmit the cyclic data and the packet data. Upper limits may be set to capacities of the cyclic data and the packet data which are capable of being transmitted each time the token is acquired.

Transmission method and system thereof

A transmission system which includes a plurality of reproduction nodes connected to each other in a cascade connection via a communication line. Each node includes a timing extraction circuit for extracting a timing signal from a signal received via the communication line, a discriminating circuit for converting the received signal into a digital signal according to the timing signal, and a processing circuit for processing, based on the timing signal, the digital signal outputted from the discriminating circuit and outputting the processed digital signal to the communication line. The timing extraction circuit includes a signal delay unit for supplying the timing signal with a signal delay time greater than a delay time occurring in the processing circuit.

Transmission system constituted of multistage reproduction nodes

A bridge apparatus for interconnecting networks in which at least two networks including a plurality of stations are connected, and which, when a transmission frame including an identifier of one station and an identifier of another station of a destination is received from the one station, forwards the transmission frame to a network to which the another station belongs based on the identifier of another station. A processor of the bridge apparatus for interconnecting networks performs delivery control of the transmission frame using an information which has been read out of an address check circuit for identifying the network to which the another station belongs with the identifier of the another station which is included in the transmission frame. The address check circuit comprises at least one hash memory in which hash computation results of respective addresses have been stored at respective address positions, and an address memory for storing a plurality of address informations showing a corresponding relationship between identifiers of respective stations and identifiers of respective networks at respective address positions.

Bridge apparatus with an address check circuit for interconnecting

A signal transmission system comprising an apparatus which inhibits the repeating in the opposite direction during reception and transmission of frames and which monitors the number of frames which were outputted in one direction from a repeater and the number of frames which were returned from such direction, whereby a destruction and circulation of the frame are inhibited without reducing response speed of a signal.

Signal transmission system having a star coupled repeater

A looped data transmission system has a pair of looped transmission lines forming two transmission systems having different transmission directions, and a plurality of stations including at least one control station connected to said transmission lines of the two transmission systems. If a fault occurs in the two transmission lines of the two transmission systems in the same section, a loopback configuration is established such that stations adjacent to the faulty section send signals from one system back to the other system. With the loopback configuration being established, the stations which have received supervisory signals sent from a loopback end station send them back to the transmission line of the other system. When one of the loopback end stations has received a supervisory signal from the direction of the faulty section, it is judged that a portion of the faulty section is recovered, and the result of the judgement is communicated to the control station.

Method of detecting recovery from fault in a data transmission system

A loop type data transmission system based on a token pass principle, wherein a station whose transmission of data is completed passes therethrough a token to the stations located downstream. The station demanding the transmission acquires the right of transmission when received the token, to perform data transmission with a given station. The token signal is classified into a free token representative of the freedom of the line and a busy token representative of occupation of the line. Among a plurality of stations, only one station is destined to execute detection of transmission failure and remedy thereof. This one station is adapted to convert the free token detected upon reconstitution and repeating of the received information into the busy signal and subsequently re-send the free token. The station having sent out the free token after the completed data transmission is transferred to the state for reconstituting and repeating the received information when the busy token returns to that station.

Loop type data transmission system

This invention discloses a loop-back control method for loop-type data transmission systems in which, when a trouble occurs on both transmission lines of two systems, two stations adjacent to the trouble region return signals toward a control station in response to a command from the control station, thereby to separate the trouble region and continue the operation. According to this invention, when the control station detects the occurrence of a trouble on the transmission lines of the two systems, it sends out a broadcast command to search for the trouble point to the transmission lines of both systems and thereafter a loop-back command is issued so that the stations adjacent to the trouble point can loop-back the transmission.

Reconfiguration control method for a loop-type data network

A loop type data highway system in which a plurality of data transmission control stations (abbreviated herein as stations) are connected in cascade to a loop transmission line. Each of the stations responds to a polling frame inquiring of request for reservation of the transmission line. The polling frame is composed of a first field for inquiring of the line reservation request and a second field indicative of whether the line is reserved or not. Each station receives signals inputted from the upstream side along the line and sequentially repeats them to the downstream side along the line without delay. In the station having the line reservation requests, a pattern representative of the line reservation is written in the second field after reception of the first field and sends out the polling frame to the downstream. When the second field as received indicates the non-reserved state of the transmission line, transmission of data is initiated in succession to the second field.

Loop type data highway system

Disclosed is an optical switch of the rotary-type in which a pair of opposing optical transmission path mounting members are disposed on the same axis. A plurality of junction faces of optical transmission paths disposed on the respective opposing plane portions of the mounting members along phantom circles which are opposite to each other and concentric with the pair of mounting members respectively with respect to the axis so that the junction faces on the respective plane portions are capable of being correspondingly opposite to each other. When the pair of the mounting members are relatively rotated about the axis, the facing mates of the opposing junction faces of the optical transmission paths are changed over to switch the optical transmission paths. In the case where an optical path relay member is interposed between the pair of the optical transmission path mounting members, the optical transmission paths can be switched by only the rotation of the optical path relay member.

Rotary type optical switch

The periodicity of an input signal is monitored by means of a re-triggerable one-shot multivibrator. When an input signal interruption is detected by the output of the multivibrator, the state of the input signal interruption is held to interrupt the transmission until a phase locked loop is demodulated. The transmission is not opened until the phase locked loop is brought into its synchronous state.

Loop type data highway system for data transmission

In an interrupt control system for a data processing unit for microprogram control including a processor constructed dividedly between an arithmetic unit and a control unit, a signal representing the absence or presence of an interrupt request to be performed is applied to the control unit so that said control unit reads a microprogram for the interrupt processing from a memory in response to said signal, and said arithmetic unit judges an interrupt source on the basis of the microprogram read out from said memory and performs processing in accordance with the interrupt source.

Interrupt control system

At the transmitting side of a data communication system, data to be transferred is converted to digital pulse-coded transmission data including a combination of two pulse signals whose pulse durations are different from each other. The pulse duration of the digital pulse-coded transmission data is detected to change the amplitude level of the digital pulse-coded transmission data so that the frequency-attenuation characteristic of signals in a transmission path may be compensated in accordance with the detected pulse duration. This modulated transmission data is sent through the transmisson path and is demodulated at the receiving end of the transmission path.

Growing community of inventors

Katsuta, Japan

Sadao Mizokawa