A excerpt from 2010: A Space Odyssey 2:
The scientist tapped out a code on the board, switching Sal’s inputs to the memory with the highest security rating. No one knew that he talked to the computer on this circuit as he never could to a human being. No matter that Sal did not really understand more than a fraction of what he said; her responses were so convincing that even her creator was sometimes deceived. As indeed he wished to be: these secret communications helped to preserve his mental equilibrium—perhaps even his sanity.
A little context: Sal is a super AI who accepts human voice instructions, and talks back like having a real conversation between human beings. It is mentioned that she can even pick up her operator’s intonation.
Providing the context, the communications between "he" and Sal are actually based on talking. So even using the secret circuit, it is obvious that he will talk to Sal a lot. So why it says here no one knew that? Does the thing no one knew refer to the fact that he talked to Sal on this circuit or the fact that he talked to Sal on this circuit because he has trouble communicating with human being?
Sentence 3: I don't understand why the punctuation here is semi colon, "no matter" and the words following it is a clause, can clause be separated from other parts of the sentence by a semi colon? Actually, if the semi colon was replaced by a colon, I will have less trouble understanding this sentence.
Sentence 3: why does it says here Sal don't understand what he said at all? Or is it just saying that as smart as she appears, the super AI doesn't really understand anything anyone talks to her, not just what he said?
Sentence 4: what is that he wished to be? The thing after the colon or the sentence before? And I can't connect this sentence with the previous ones. I know the author is trying to portrait "he" as an isolated computer geek who cares nothing else, but even for a person like that, I don't see why talking to the computer on "a secret circuit" maintains his sanity.