| 摘要 |
PROBLEM TO BE SOLVED: To provide a signal transmitter which is not influenced by electromagnetic radiation even when a plurality of circuit boards for network terminating device is piled upon another in the transmitter. SOLUTION: A signal transmitter, which is constituted of a plurality of circuit boards and transmits and receives electric signals by using a metallic wire, is provided with a first circuit board 40 connected to the metallic wire and another circuit board provided on the rear surface of the circuit board 40 and connected to the board 40 through a connector 60. The transmitter is also provided with a high-voltage protective circuit 41 which is provided on the first circuit board 40 and protects the other circuit portion from a high voltage when the high voltage is impressed upon the metallic wire, and a shield pattern 42 which is formed at the portion corresponding to the portion where the protective circuit 41 is set up on the rear surface of the first circuit board 40.
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