On my MK7A - and this is just my guess based on observation - Pulse 1 flashes (~1000 flashes per KW) when energy is being used from the grid. Pulse 2 - at least for me - flashes when my solar is generating. So Pulse 1 for household energy use and Pulse 2 for solar generation. Again, not sure if the pulses indicate different things on other meters, or if you don't have solar maybe Pulse 2 does nothing? This is just what i've observed in my particular setup. By way of illustration - on a sunny day ...
