PURPOSE: To detect the detection of a starting point by providing the 1st detection section integrating a level of a reception signal and the 2nd detection section integrating the reception signal through a filter passing through a frequency component.

CONSTITUTION: In synthesizing outputs of adders A2, A3 by an adder A4 and integrating the result by an integration device 23, the level of the integration output Y is coincident with an output X of CD detection section 15 at the detection of π/π, and an output Z of an adder A5 is zero. While a noise exists or the level of the line is fluctuated, since the level of the output Y is limited in terms of frequency, the level is smaller than the output X in the range of all frequencies. Thus, in catching a point when the polarity of the final output Z changes from a negative value to '0', it is discriminated at the head of a training signal and the pull-in sequencer is started correctly. Thus, the pull-in start point is detected surely at a MODEM reception section.