| 摘要 |
PURPOSE:To reduce a synchronization time of a demodulator and to attain quick line connection control by releasing the holding state of a synchronization frequency of a carrier recovery circuit after a frequency synthesizer of other demodulator is set. CONSTITUTION:A common line signal control (CSC) circuit 4 designates a same reception channel to a demodulator 3 as that of a demodulator 2 when the demodulator 3 is not in operation. Thus, a frequency 302 and a carrier recovery device 303 are operated and synchronized with the reception channel of the demodulator 2. When the reception channel is designated to the demodulator 3 in this state, the circuit 4 turns off a hold switch 315 to allow a hold capacitor 316 to hold a just preceding VCO control voltage. Then the circuit 4 sets a parameter of a loop filter 307 and a band width of LPFs 310,311 in response to the modulation speed and the synthesizer 302 is synchronized. Thus, the synchronization establish time of the recovery device 303 is decreased and the line connection delay time is minimized. |
