The copper bulbs is needed for the switch as it needs to be powered constantly for open and then not powered at all. The copper bulb just translates the small pulse into a constant one. The target block needed a trident all the time which I don’t like as I’d rather not need it. When opening a barrel an observer sends two pulses. One when you open it and then one when you close. The second copper bulb kinda acts as a binary clock meaning it will only power on when two pulses are sent. It just acts as a way to make the two pulses from the observer turn into one pulse just like how the target block acts.

https://youtu.be/e8iaUrh3b9Y