The 545 Optical Disrupter is an optical compressor which creates an asymmetrical waveform as it compresses. It creates second-order harmonic distortion without clipping the signal.
The effect is created by compressing only the top half of the waveform. So compression occurs, but distortion is the primary function.
Consequently the expense of a gain reduction meter has been omitted. Simply apply the amount of distortion desired and consider compression the natural by-product.