PURPOSE: To make possible increasing operating speeds of a readout, etc., without increasing a circuit area by splitting substantially bit lines of a DC. signal transmission line with NMOS transistors(TRs) being normally in ONs.

CONSTITUTION: A writing voltage by a writing circuit 1-1 is written in cells 4-1, 4-2... connected with bit lines of a signal transmission line. N type TRs NTR1, NTR2... being normally in ONs on whose gates a power source voltage VDD is supplied are turned OFF by this write-in and bit lines are substantially splitted and then cells 4-1, 4-2... are read out via corresponding sense-amplifiers 2-1, 2-2.... Since this circuit is of a constitution in which bit lines are not splitted actually, this circuit becomes a signal transmission control circuit without increasing the circuit area in which operating speeds of the readout, etc., are increased.