| 摘要 |
PROBLEM TO BE SOLVED: To increase the transmission quantity of signals per unit time with suppressing the transmission power and suppress the signal interference with other electric apparatus or broadcast waves, etc. SOLUTION: A gain controller 10 variably controls the level of transmission signals matched with the phase of an AC power source voltage. For example, based on data D2 concerning with a detected noise level, the level of the transmission signal is variably controlled so that the level of the transmission signal is relatively low in a first phase section with a relatively low noise level on the AC power source voltage, but relatively high in a second phase section with a relatively high noise level. The data D2 of the noise level may be acquired periodically to periodically correct the level of the transmission signal. COPYRIGHT: (C)2005,JPO&NCIPI
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