The T3 manual doesn't mention an IR receiver. Only a wired remote.
It looks to me as though the T3 has a simple 1/8 inch stereo jack which should be easy to connect to. (I have the 50D which isn't as easy to do because it has a non-standard plug).
I believe the jack is similar to what vwlowen showed for his Nikon although Canon might have the shutter and focus as he shows or swapped.
I would recommend that you use optoisolators as he shows. You could probably get away without them but it's an expensive risk to take.
Pete