| 摘要 |
PURPOSE:To make it possible to perform an efficient adjustment of a subscriber side equipment by sending different frequencies carrier waves from the subscriber side during a prescribed period by a carrier wave outgoing control means at an adjustment time of data sending level. CONSTITUTION:From a time when a transistor 46 is under a shutdown condition, upon coming a transmission request signal (RST) until a time when a terminal voltage of a capacitor 49 rises and exceeds a Zener voltage of Zener diode DZ, a carrier wave frequency is set to f1 during an output terminal potential of invertor 44 is low level. Furthermore when a transmission frequency selective signal (SEL) rises to a high voltage level as the terminal voltage of the capacitor 49 increases to the above-mentioned Zener voltage, a transistor conducts and the carrier wave frequency changes to a frequency f2 which is decided by a quartz oscillator X2. Accordingly in the case where data are usually send to a upstream, once a frequency wave is send beyond the RST signal period, the carrier wave of frequency f1 is stopped automatically and its carrier wave frequency is changed to f2.
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