Why would my phone chirp everynight at 9:20?

So I plugged in a cheapie phone (couldn’t have cost more than $10 if that) in my bedroom so I don’t have to go running into the living room whenever I get a call. It’s one of those that basically sounds like a cricket. But I’ve noticed that every night at some point between 9:15 and 9:25, it will make a pathetic little half a chirp, like a cricket who’s drunk or something. No one is calling since my other phone isn’t ringing. What’s going on in my apartment complex or phone lines that could cause this timely occurance?

The Master Speaks.