Here is a list of witness channels we used in O3 to subtract calibration lines at LHO:

SUS-ETMX_L1_CAL_LINE_OUT_DQ

SUS-ETMX_L2_CAL_LINE_OUT_DQ

SUS-ETMX_L3_CAL_LINE_OUT_DQ

CAL-PCALY_TX_PD_OUT_DQ


and at LLO:
SUS-ETMX_L1_CAL_LINE_OUT_DQ

SUS-ETMX_L2_CAL_LINE_OUT_DQ

SUS-ETMX_L3_CAL_LINE_OUT_DQ

CAL-PCALY_RX_PD_OUT_DQ