Which installation is characterized by circuits being supplied directly from an overhead source?

The installation characterized by circuits being supplied directly from an overhead source is indeed correctly identified as the feeder circuit. In electrical distribution systems, feeder circuits are responsible for carrying power from substations to different areas, where they are often connected to overhead lines. This setup allows for efficient power distribution over long distances, directly utilizing overhead sources which may include power lines.

The other options refer to different types of electrical configurations. URD (Underground Residential Distribution) installations involve distributing power through underground cables, which is the opposite of overhead supply. Loop installations typically refer to a network configuration where multiple paths for power are provided, offering redundancy. Radial installations are characterized by a tree-like structure where feeders branch out to individual loads, but they do not specifically denote the use of overhead lines directly supplying the circuits.