When I was a student, I often visited friends in a rental apartment. Ordinary panel house. Long staircase on one side two apartments and on the other. And usually the entrances to the apartments were flanked by a wall making a common little corridor for two apartments.

So here. Leaving friends and just going to the elevator, it was already heard how he was driving, but they still pressed the button and waited for him to arrive.

But then everything changed. One day, going to school, after overnight, and very late I went out to the site, parallelly crawling in the bag, forgot to press the lift call button. I was surprised by an empty elevator. I did not give it special importance.

Then for the sake of interest decided to check, suddenly it will repeat. I go out again, standing in front of the elevator, I hear it coming, coming, empty. I began to be scared.

After the raids of the neighbors from above, said it was good to smoke on the balcony, to her all "fly" and "smell", began to run to blow up the stairs.

Almost every time we got out of the apartment, there was an empty elevator.

As it turned out later, the neighbor turned out to be an electrical engineer, who worked all his life at the factory and developed automatic systems for conveyor production.

During the repair of the entrance, he laid the wire from the lift call button to the "curve" where the apartments were fitted. He put in it some relay, or something else (shortly that closes the chain from movement).
Upon leaving the apartment, this illusion in some fairy (for me) way caused the elevator. While the neighbor (pensioner) came out of the apartment, closed it, and went, the elevator was already on the floor.

We learned this after we went out to smoke on the stairs with this Grandpa, and then he told us the great mystery of drums.

Engineers will not disappear.