When you're talking on the phone and you have a call waiting feature on, you hear a beep when there's another person calling you.
Student or Learner
I want to know the meaning of "beep in" while someone's calling
When A hang the phone, he said B beep in
I think this is kind of interruption during calling
Give me some details please
Our conference calling system announces that someone has joined the conference call with a beep.
I agree that the call waiting feature is the more likely situation, but it's possible that someone else "beeped in" to mean joined the call.
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.