| 摘要 |
PROBLEM TO BE SOLVED: To achieve excellent communication on transmission lines with different losses between various cars by using IEEE 802.3 standards in a communication system for railroad cars. SOLUTION: The communication apparatus performs LAN communication between a central unit provided in one of a plurality of railroad cars connected together and each of terminal devices provided in a plurality of other railroad cars. A gain of a communication signal to be transmitted from one apparatus to the other apparatus is adjusted and a reference signal for detecting a transmission line loss is superimposed on the communication signal. At a receiving side, a level of the received reference signal is then detected and on the basis of the reference signal level, the gain of the communication signal is controlled. Even when terminal devices different in distance of the transmission line are connected, the gain of the communication signal can be determined while taking into account influences of the transmission line loss, thereby obtaining a stable communication system. COPYRIGHT: (C)2011,JPO&INPIT
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