buzz in

verb2

1. •
   (informal) To open a remote-controlled door to allow (a person) to enter after sounding the doorbell or buzzer.

   • I'm going to buy some more coffee. Could you buzz me in when I get back?
2. •
   (informal) On a game show or similar competition, to press the buzzer to provide an answer.

   • It was the first contest to employ a "lock-out device": whichever contestant buzzed in first automatically shut the other out. — 1979