/diy/ - Do It Yourself

Hi guys,
newb here
Q: I'm working at a small office in a multi-story residential building, and we have the issue that if someone rings our unit's doorbell (at the buildings main entrance) we've to run to a 2-way-intercom-door-buzzer box to buzz them in.

my idea was it to have it automated, as the door bell and buzzer and 2-way intercom are all in one box, that - and here's where my newbness shines - "some" IC, that has the ability, that if a current is on a line (the door bell ringing) that the IC waits like 5 seconds before it closes the buzzer-in circuit for the buildings main entrance door.
preferably the IC has a line for a manual on/off switch too.

I'm sure something like that exist, but I don't know what search terms to use to find the correct thing.

thanks-a-thon in advance