A notch at 331.9 Hz in now turned on in the LSC-DARM2, FM4. The change was accepted in SDF_OVERVIEW "safe.snap" and "OBSERVE.snap".

This filter suppresses the DARM loop at PcalY calibration line frequency that is used to track the optical gain and the coupled-cavity pole frequency.

In an earlier report we pointed out that the notch was switched off during ER9 (see LHO alog 29108).