| 摘要 |
PURPOSE:To ensure the initial acquisition without slowing down a sweep speed even when the transmission speed is low by switching a threshold level discriminating the frequency of occurrence of an error pulse into two high/low stages from a conventional threshold level into a higher threshold level and comparing the frequency of occurrence again. CONSTITUTION:A threshold level controller 17 switching a threshold level to discriminate the frequency of occurrence of an error pulse into 2 stages, 1st/2nd high/low stages connects to a sweep controller 16 and the sweep controller 16 applies comparison discrimination to the frequency of occurrence of an error pulse S8 based on the two stages of threshold levels. That is, when the frequency of occurrence of the error pulse is lower than the 1st threshold level, the sweeping is stopped once and the sweeping is restarted and continued when the threshold level does no reach the 2nd threshold level or below after the lapse of a predetermined time. Thus, even when the transmission speed is slow, the initial acquisition is surely implemented without reducing the sweep speed. |
