In the SPD testing world there has always been a conflict between those who want to test the SPD “as is” and those who want to take the SPD apart to put copper shorts and the like inside – “open the box”.
Recently one manufacturer, who produced a component that combined an MOV and GDT, was frustrated by a test laboratory that wanted to separate the component into its MOV and GDT parts and test each independently - “open the box”. It mattered little to the test laboratory that the performance of the separate parts would not be the same as when in combination.
This led to the thought “What is the difference between an assembly, integrated circuit and hybrid protector”. It may come as a shock to some that an integrated circuit doesn't need to be something like you get from companies like Intel or Texas Instruments. How the IEC defines in this area is reviewed here, concluding with some recommendations.