LG LHD625 Service Manual page 70

10) Tracking control related signal (System checking)
PU_DET
TRO
T-
T+
PU_DET
PU_DET
TRO TRO
T-
T-
T+
T+
DVD
PU_DET
TRO
T-
T+
CD
37
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40
37 : This signal can see using special debug program
37
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38
39
40
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IC500
37