This is the reference level of the calibrator’s output, indicated on the device itself or in the corresponding datasheet. A typical value is -94dB.
This is the offset applied to RMS</link> dB values in order to obtain dB SPL</link> readings. It is determined automatically by the calibration procedure.
Press this button after having insert the microphone into the calibrator socket and activated it in order to determine the SPL</link> trim value.