It took Sulu a moment to realize that Ianto's voice was... well, in his head instead of out-loud, but when he did, he beamed like a kid who'd just discovered Santa Claus really did exist.

"Oh, wow." He felt the pendant at his neck and barely restrained himself from making a total idiot out of himself. There were a few telepathic alien species in his universe, but humans never could figure out how to do it themselves - at least, in a way that wasn't immediately dismissed as a hoax. "This is amazing! - Is it only one way?"