Hitachi, Ltd.

Hitoshi Fushimi

Seiichi Yasumoto

Takuji Hamada

Jushi Ide

Masahiro Takahashi

Sadao Mizokawa

Masakazu Okada

Hiroshi Tomizawa

Hiroshi Kuwahara

Kotaro Hirasawa

Ken Onuki

Yoshiji Ito

Hiroshi Kaita

Yasuo Hosoda

Hiroaki Ohnishi

Tadaaki Okada

A loop transmission system having a plurality of data processor connected through respective transmission station with a common loop transmission line is disclosed. This system has a concentrator connected with a plurality of transmission stations through respective loop transmission lines. The concentrator changes the order of connection said loop transmission lines thereby to change the order of connected of said transmission stations on said loop transmission lines.

Loop transmission system having plural stations connected in a variable

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

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

A duplex transmission control system having active and inactive systems for totally controlling a looped transmission line on which computers and terminal devices are connected through respective stations. Each transmission control unit is operable to transmit and receive specific data related to the priority level specified for each unit. Each transmission control unit suspends the transmission of the clock for a certain period in response to the detection of the clock suspension, then transmits the specific priority data. When a transmission control unit detects its own transmitted signal, it is designated as the active system when another transmission control unit receives the signal defining the active system, it is designated as the inactive system.

Loop data transmission control method and system

A dual loop type data highway system comprises a data highway having at least two loops for data transmission and reception, a plurality of data transmitting/receiving stations serially connected to the data highway and a control station serially connected to the data highway. The data transmitting/receiving stations each have means for detecting the beginning of a transmission cycle, one for each of the loops, and the control station has, one for each of the loops, means for detecting the end of the transmission cycle and means for permitting the transmission/reception of data between specified two of the data transmitting/receiving stations during the transmission cycle by polling, whereby an effective transmission rate is increased without considerable increase of hardware.

Dual loop type data highway system

A central station and a plurality of transmission stations are connected in cascade by a serial transmission line, and constitute a looped data highway system. The central station controls the whole system. The system allows the transmission station having a data signal transmission request to send out a data signal by means of a normal polling signal, but only the station having sent out the data signal by means of the preceding normal polling signal is allowed to send out the data signal again in response to a retry polling signal.

Data transmission system and method

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

A loop type data highway system in which a plurality of data transmission control stations (abbreviated hereinafter as stations) are connected to a single loop transmission line for data transmission and reception between any desired ones. A transmit station transmitting data makes a compare check to compare successive predetermined unit lengths of the transmitted data with the corresponding ones of the data returning after travelling round the loop, thereby detecting an error occurring during the data transmission when non-coincidence exists therebetween. A receive station receiving the data monitors the number of data words to be received, thereby detecting an error occurring during the data transmission when a data transmission end signal is detected prior to arrival of all the data words. Upon detection of the error occurring during the data transmission, the transmit station transmits the data transmission end signal to the receive station to inform the receive station of occurrence of the error.

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Hitachi, Japan

Hitoshi Fushimi