An operator car is typically located where the jib meets the tower. The tower crane operator sits inside of this car and uses a series of controls to swing the jib and move objects. An individual on the ground or within the building oversees the process of fastening objects to the cables of the tower crane. This individual is known as a rigger, and he or she uses radio or hand signals to communicate with the crane operator.
There are two basic types of tower cranes, and they are generally categorized based on how they are constructed. A standard tower crane is assembled using a smaller supplementary crane. A self-erecting tower crane contains a hydraulic base, which forces sections of the tower up to a specified height. A secondary crane is used to attach the jib before the hydraulic mechanism is activated.Tower cranes are often rented or leased for the duration of the project. They are known for their high cost, and also for the high number of safety precautions required to prevent collapse or injury. In very tall or complex buildings, the tower of the crane may be left in place, where it becomes a permanent part of the building. This allows builders to successfully complete a project without the risk of damage caused by trying to remove a crane from a finished building.