How tower cranes work?

All Tower Cranes consist of the same basic parts: 

Tower cranes in general are composed of three main parts: the base, the Mast Section or tower, and the slewing unit.

On top of the slewing unit are three parts:

1. The long horizontal jib (or working arm), which is the portion of the crane that carries the load. A trolley runs along the jib to move the load in and out from the crane's center:

2. The shorter horizontal machinery arm(or counter jib), which contains the crane's motors and electronics as well as the large concrete counter weights.

The movement of the crane is controlled from the operator’s cabin. Within the cabin, you’ll find the operator’s chair with joystick controls, electronic monitoring devices, and communication systems. Many cabins come with climate control to ensure a comfortable work environment. The operator cab is part of the slewing assembly.