A tethered drone represents a specialized category of unmanned aerial systems that fundamentally redefines endurance and reliability by physically connecting to a ground-based power source via a specialized cable. This tether, often a composite containing electrical conductors and fiber optics, serves as a continuous lifeline, delivering perpetual power and enabling secure, high-bandwidth data transmission. The system's core architecture consists of three integrated components: a ground power unit—which can be a generator, vehicle power system, or grid connection—that supplies energy; the tether cable itself, engineered for lightweight durability and efficient transmission over operational altitudes typically ranging from 50 to 200 meters; and an onboard power conversion module that conditions electricity for the drone's propulsion and payload systems. This configuration solves the most significant limitation of battery-powered drones—limited flight time—by enabling operational endurance measurable in dozens of continuous hours rather than minutes. The persistent aerial presence created by this technology makes it invaluable for applications requiring uninterrupted oversight or connectivity, including critical infrastructure security, large-scale public event monitoring, emergency response coordination, and temporary communications relay in disaster scenarios. While the operational radius is constrained by tether length, eliminating traditional free-flight mobility, the trade-off delivers unmatched stability and persistence. The integrated fiber optics ensure jam-resistant, low-latency data links for real-time high-definition video and sensor data streaming, far surpassing the reliability of wireless connections in congested or contested electromagnetic environments. Modern systems incorporate sophisticated tether management, automated launch and recovery, and fail-safe protocols to enhance operational robustness. As technology advances, tethered drones continue to evolve as dedicated aerial platforms for persistent sensing and communications, establishing their indispensable role in security, defense, and industrial applications where mission success depends not on mobility, but on unwavering aerial presence and guaranteed data links.