Hitachi, Ltd.

Hitachi Process Computer Engineering, Inc.

Hitachi Cable, Inc.

Masato Satake

Sadao Mizokawa

Hisayuki Maruyama

Seiichi Yasumoto

Ken Onuki

Toshiyuki Murakami

Toshihiko Uchiyama

Junji Fukuzawa

Hisao Ogawa

Osamu Anbo

Jushi Ide

Masanori Kogawa

Naomasa Hanano

Toshio Ishihara

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 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

Growing community of inventors

Ibaraki, Japan

Masato Satake