andrew.lundgren@LIGO.ORG - posted 07:52, Tuesday 13 December 2016 - last comment - 14:09, Tuesday 13 December 2016(32503)
The PSL answers the call, once again
Andy, Tom Dent, Josh Nutsinee (alog 32159) and Patrick (alog 32163) both reported a string of glitches during their shifts on Dec 4th. These showed up again in connection with an investigation into some PyCBC loudest events. At Tom's suggestion, we listened to the PSL microphone, which is one of many PEM channels seeing a huge disturbance at these times. I've attached the wav file of the PSL center mic. It seems like the PSL intercom (or some other phone) rings twice and afterwards forwards the call somewhere else. You can hear a faint third ring, and Josh has another file where talking can be heard after the faint ring. When this happened at LLO during an ER, (L1 alog 8451 the intercom would answer and then make a busy signal. It's not clear why we haven't seen this more often, or when the intercom could have gotten connected. This is in the middle of a long stretch of science mode. Edit: To be clear, the loud rings make something very strong in DARM. We're investigating to what extent the quieter stuff shows up.
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Here's a spectrogram of the PSL Mic annotated. The second set of more distant rings followed by auto answer starts around second 19. Also attached is the STRAIN spectrogram. The coupling to STRAIN is clear for the PSL rings and it looks like there is faintly also the second set of rings seen. Also attached is the longer Wav file with the speakerphone and talking for the first call and the rings of the second call a minute later.
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Opend FRS Ticket 6923
Both PSL Phones have been disabled, see LHO aLOG 32508. FRS Ticket 6923 closed. Tagging other relevant subsystems to envoke L-Mail.