Now, inside we've got motion detectors,
INFRARED sensors...
The Big Bang Theory Season 3, Episode 13
Run an INFRARED repeater,
photocell here, emitter here, easy-peasy.
The Big Bang Theory Season 1, Episode 2
What's up with the INFRARED cameras?
The Big Bang Theory Season 4, Episode 18
The optics are great.
It's got INFRARED technology.
The Big Bang Theory Season 6, Episode 21