| 摘要 |
PURPOSE:To obtain high transmission efficiency in average in any frequency of transmission by using in switching the CSMA/CD system having high transmission efficiency and the DSMA/CA system in any case while the frequency of transmission request from each device is divided into a low or high. CONSTITUTION:A transmitter 2 consists of a reception circuit section 3 analyzing a packet frame flowing in a transmission line and discriminating whether or not the frame is a frame to be fetched to the own transmitter, an access method switching control section 4 measuring the frequency of signal flowing a common transmission line 1 and discriminating which of the CSMA/CA and the CSMA/CD has better transmission efficiency, a transmission circuit 5 accessing the common transmission line 1 with the commanded access method and sending the transmission data, a transmission/reception buffer receiving the frame to be fetched to the own transmitter from the reception circuit section 3 as a reception data and a transmission/reception control section 6. The transmitter 2 detects the frequency of a signal flowing to the transmission line, and when the frequency of signal is high, the CSMA/CA system is selected and when lowered, the CSMA/CD system is selected.
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