| 摘要 |
<p>An on-hook/off-hook detector circuit (61) detects the voltage level of a telephone line (C) to determine whether the speech band is in on-hook or off-hook state, and produces a state signal (81). TEQ (63), FEQ (66) and constellation encoder gain scaling (67) perform adaptive equalization, bit distribution and gain distribution in time and frequency regions for data communication by using separate tables (75-80) depending on the state signal (81). Since the telephone is not used in on-hook state, the transmission subcarrier band for communication is shifted near, or expanded into, the speech band.</p> |
