The process of cylinder exchange
The exchange of a gas cylinder requires to use a special key bought in a trade point. The key should be suitable for a particular kind of cylinder, e.g. the A key allows to exchange cylinders 11kg, and the B key to exchange cylinders 7,5kg.
Buy a key correspond to the kind of the gas cylinder you want to exchange,
Find boxes in the device that correspond to the kind of your key.
Insert the empty cylinder to the empty box. Use the special mechanical key bought earlier, by turning it in the lock.
The blockade securing the door is released and the door may now be moved, thereby securing the deposited cylinder and opening access to the full cylinder.
Take out the full cylinder after moving the door.
A new client will be able to deposit his/her empty cylinder in the box, which stays open after the previous client.