After much testing and frustration here's what I've learned.
-A clock is just a device that pulses at a set interval, it knows when to pulse based on server ticks (thats why its called a clock).
-You can craft a clock (search for 5 clock) using just standard redstone or using the MC0420 (self triggered).
-Any IC that requires a clock input (p-detection mc1272 included) does so because it will only check states when it
toggles from low to high power. This is why your P-detection will toggle on when you are near it and NOT toggle off. It needs another pulse (low to high) to check the state to see if you are there.
-The problem with this is pretty obvious, which is why we have self-triggered IC's. Self triggered circuits have a clock incorporated into them already, so the detection circuit just detects if you are there every 'x' server ticks (not sure the exact number) and can't be turned off. The problem is that the clock is always running and has the _potential_ for causing server lag. I know there are other servers with as many users that utilize selftriggered IC's but I'm not a server admin and won't comment on policy, I'm sure they're doing what they can.
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I have a P-detection door currently working, however its far to complex and in mass, would probably cause more lag then just having the simple p-detection self triggered circuit. You use a pressure plate to provide current to the P-detector AND to on part of a 2AND IC. The other side of the 2AND is provided by the P-detection. If both are true the AND circuit provides power to the iron doors. If you use two Iron doors, annoyingly, one will be open while the other is closed at rest, so you must use a NOT circuit to invert the current and give an opposite state (if anyone knows an easier way let me know).
The result is that the state is checked for a player any time the pressure plate is pushed. Yes, it thinks you are there when you arent, but if another player shows up, the door will momentarily open, then close once the check to see if you are there is over. Again a possible exploit, but no real way around it.
Also due to the weird issue with iron doors resting at opposite states, if the server restarts, the odd resting door will default to open until current is run through it once to activate the "not" circuit (again let me know if you know how to fix this).
If anyone wants to see it, message me in game and you can see the door.
--edit--
My understanding is that ALL self-triggered IC's are disabled, can an admin confirm this? @
Kainzo .