Patent ID: 7385387

Claim:
A signal processing circuit of a rotation detecting device that includes a rotor rotatable with a rotating object, a rotation sensing unit for providing a bi-level first rotation signal (Sa) in response to rotation of the rotor, said signal processing circuit comprising: a reversal signal forming means, connected to said rotation sensing unit, for providing a bi-level reversal signal (Rev) changing from one level to the other in response to a change of rotation direction of the rotor; a level-change-prohibiting section, connected to said reversal signal forming means, for forming a level-change prohibiting signal (Ce) to mask the first rotation signal (Sa) during one pulse width from the first rising edge to the first falling edge after the change of the rotation direction of the rotor is detected; and a rotation data processing means, connected with said level change prohibiting section and said reversal signal forming means, for forming a triple level output signal (OUT 2 ) having triple-level pulses that synchronize with the pulses of the first rotation signal (Sa) except for first one of the pulses being masked after each change of the rotation direction and change voltage level from one level to another when the rotation direction changes one direction to the other direction.