So simple
In your flat the entryphone goes buzz. If you can hear a similar muffled buzz from flats above, below and to the side you know that someone wants to gain access to the building. They're not, probably, after you. Now, if you are feeling charitable and not in the middle of some personal hygiene ritual or atop a stepladder (and 99% of the time you are) you might pick up the phone. The format is not polite, the format is short and does not start with a greeting. "Yes?" or "Who?" are common. The answer is usually short too. It may be the neighbour's daughter with some long explanation about why she has no key or it may be the electric people who need access to some dark and distant part of the building but usually it isn't. Most often it's the postie. They announce themselves with whatever is their political take on the Spanish for postal carrier. No more conversation you just buzz them in. Now, even if it isn't the postman/postwoman but it is, ...