Photosensitive= light sensing

E.g.

Turns on when day, ff when night

Anywhere I can see an example?

If there's a IC for this, I could use this in my vault for lighting. I already made a light system there.

There's several ways to make light sensing lighting. The wiring should be simple enough, but the light detector is a little harder. You can use grass, or a mushroom, connected to a BUD (which detectes block updates, hence its name "Block Update Detector") switch, thats connected to several redstone lamps. The grass will grow during light, and the mushroom will pop out when exposed to light. Another way to do it, is by setting a long row of redstone repeaters in a loop, that turns the circuit on and off every 10 or so minutes (however long a day lasts in Minecraft). There's a lot of videos on youtube explaining how to do the three methods. I can't find a reason you would want to do this though. Why not just leave the lights on?

In reply to the posts

There is an IC have a look on craft book wiki

I know how to make it and the redstone delay doesn't work due to server lag

And it is just cool

Lol

Anyway I just want to see what it would look lieu and work like on the server

redstone delayers are delayed in addition to server lag... so it still comes out to the same time. How do I know? I use a series of repeaters to delay a crusher for blazes to bring them to a half health. It still works even on server lag, because their damage is lagged, and so is the time.

Also, if we have an IC for this please post on how to utilize it (or link to the wiki page), as that would be a great addition for an adventure zone I'm creating at the moment.

as to the question of why would you not just leave the lights on all the time... there are a bunch of reasons. if you wanted working streetlights or a shop that came on during the day for a more immersive feel come to mind right off the top. Maybe you have a huge cave and can not see the day/night cycle outside so you set up a system that has strategically placed lights that are on during one cycle or the other so you know what it is outside. (been trying to come up with a way for this myself for this reason). i wish they would just include a photosensitive redstone switch.

If you wold please read that again as he states in a loop which is ALWAYS stopped by server lag

Other than that I agree with you that it doesn't delay direct currents only repeated ones

IC's list here

http://craftbook.sk89q.com/wiki/Integrated_circuits

(use signs)