Overhead wires are a common sight in urban areas where power supply is required for transportation and business activities. In technical terms, overhead wires are called catenary wires or trolley wires. These wires carry electricity to power streetcars, trams, trolleybuses, and electric trains. Some other terms used to describe overhead wires are contact lines and pantograph wires. These terms refer to specific parts of the system used for collecting or distributing electric power. In addition, some cities use the term "trolley-pole" wires or "catenary suspension" wires to describe the overhead electrical system. All of these terms are used interchangeably to refer to overhead wires, which are integral to modern-day public transit systems.