| 摘要 |
PURPOSE:To correct the frequency offset of a signal by adding an out-band signal to a data signal to be sent, using the signal to estimate the frequency offset of the line at the receiver side and discriminating the locked signal. CONSTITUTION:A data signal from a terminal equipment is inputted to a modulator 11 and inputted to an adder 13. A sinusoidal wave generator 12 generates an out-band sinusoidal wave, which is outputted to the adder 13. The adder 13 sums up the two signals to generate a transmission signal, which is outputted to a telephone line 20. The transmission signal from the line 20 is inputted to a multiplier 32 and a band pass filter 37. The multiplier 32 multiplies the sinusoidal wave from the sinusoidal wave generator 31 with the signal from the line 20 and outputs the product to a low pass filter 33. Since the sinusoidal wave fed at the out-band in the transmission section 10 is subjected to frequency offset equal to that of a modulation wave from the transmission section 10, the signal is demodulated by an oscillator 31 of the reception section 30 and the frequency offset is extracted by inputting the signal through the filter 33. |
