PURPOSE: To detect the moving direction of a minute movement of a mouse by using a phase detection circuit so as to detect a phase difference of the leading and trailing edges of each of two rectangular wave signals generated by the movement of a mouse so as to sense the moving direction and a pulse representing the movement.
CONSTITUTION: The two rectangular wave signals generated from mouse signal input terminals 1, 2 through the movement of a mouse are inputted respectively to leading and trailing edges detection circuits 3, 5 and 4, 6, where the leading and trailing edges of the signal are detected. An OR of high level pulses generated by the circuits 3W6 is operated by an OR gate 7. Moreover, a delay circuit 8 retards an output of a gate 7, the leading and trailing edges of pulses from the circuits 3W6 are fed to AND gates 12W18 and the signal from the terminals 1, 2 and the inverted (9, 10) signal are subject to logical operation. Moreover, the signal is processed by OR gates 19, 10 and an FF 21, the output and the output of the gate 8 are processed by an up-down counter 22 to detect the moving direction of minute movement of the mouse.