The image shows an AC wiring example which I believe is incorrect. When switching AC you should switch the hot wire which for AC in the United States should be the black wire. White would be neutral. Please confirm that in the example you are showing you should actually have black (hot) running into “Comm” then black (hot) running out of NO or NC to the appliance, a lamp bulb in this example. Then from the other side of the bulb white (neutral) should then return to your grounded neutral bar. In the US for AC a red wire would normally be another hot wire to make 220.
@tkurtz great question… disclaimer: I’m not a licensed electrician, and you should check your country and city’s building codes to know for sure. Yes that’s true typically the HOT (black… but not always black) wire is the switched wire to a lamp or fan. The HOT gets switched through a wall switch. However, the US 110VAC outlet typically has both HOT (the small prong) and NEUTRAL (the large prong) and GROUND (the roundish prong). Yes the HOT should be switched, presumably so that when it’s off and you are unscrewing the light bulb you are MORE protected. You CAN still get shocked by the neutral wire because you should not assume you are grounded to the same point that the neutral bus bar is, there can be a differential. Make sure you use a cord that has a polarized connector so you cannot invert the plug later on. Finally, BE SAFE and unplug the entire circuit before changing the lightbulb or fiddling with the AC load or relay shield
Reference on outlet types:Don't take my word for it (or Wikipedia's for that matter)! I assume no liability for your wiring mishaps. AC is dangerous. Be safe, be smart! Hiring a certified electrician can save your life.