2 and a dc power source connected to an end of the resistor r 1 the rotation data processing section 60 provides a triple level signal out 2 whose level changes as the rotation direction of the rotor 80 changes the nand circuit 62 has input terminals respectively connected to the d flip flop circuit 45 and the inverter 53 via the inverter 61 and the nand circuit 64 has input terminals respectively connected to the d flip flop circuit 45 and the inverter 53 the nand circuit 62 controls the transistor tr 1 via the inverter 63 and the nand circuit 64 controls the transistor tr 2 via the inverter 65 therefore the transistors tr 1 tr 2 turn on or off to provide the signal out 2 which is shown in fig3 and 4 the signal out 2 has three levels that is h high level l low level and m middle level when the rotor 80 rotates in the normal direction the level of the reversal signal rev is u201c 0 u201d as shown in q of fig2 or 4 in the meantime the level of the output signal out 2 of the rotation data processing section 60 becomes u201c h u201d as long as the level of the.