Rectilinear laser vibrometers can be calibrated in accordance with ISO 16063-41:2011 if they are designed as laser optical transducers with, or without, an indicating instrument to sense the motion quantities of displacement or velocity, and to transform them into proportional (i.e. time-dependent) electrical output signals. These output signals are typically digital for laser vibrometer standards and usually analogue for laser vibrometers. The output signal or the reading of a laser vibrometer can be the amplitude and, in addition, occasionally the phase shift of the motion quantity (acceleration included). In ISO 16063-41:2011 the modulus calibration is explicitly specified.