Mystery of the two buildings

Once, when applying for a job (I was not accepted at Schneider Electric), I passed a funny intelligence test. This test didn't pass right off the bat, because I didn't meet the allotted time, but I decided.
Task condition:
1. There are two buildings
2. A cable connection consisting of three cores is laid between the two buildings
3. Each building has a bell (220V) and a button with a normally open contact
4. Two cores (220V and neutral) are connected to the right building

Problem statement:
How to lay a connection diagram inside these two buildings so that when you press the button in the left building, the bell in the right building sounds, then vice versa?

The riddle about two buildings

# ElectricalRiddle