This PV is the total transmission of all the filters together, which is useful for calculating the transmissions of the configurations matrix. It is not a readback of the transmission through the current filter configuration ( which requires awareness of the current filter position states ).
https://github.com/pcdshub/hxr-attenuator/blob/dabdc3f68ebb032dda78351d8f71b7ef66c6d46f/caproto/ioc-satt-dev/db/system.py#L10
This PV is the total transmission of all the filters together, which is useful for calculating the transmissions of the configurations matrix. It is not a readback of the transmission through the current filter configuration ( which requires awareness of the current filter position states ).