Which of the following devices indicates depth of a cable?

The electromagnetic detector is the correct answer because it is specifically designed to locate and measure the depth of underground cables. This device uses electromagnetic fields to detect cables, providing not only the location but also the depth of the cable. It works by sending a signal through the cable, which can then be picked up by the detector, allowing the lineman to ascertain how deep the cable is buried.

In contrast, a cable spear is used for penetrating or accessing cables, typically in service applications, rather than measuring their depth. A fault indicator is designed to signal the presence of faults in electrical circuits, indicating areas where issues may be present, but does not provide depth information. A radial circuit refers to a type of wiring configuration but doesn’t pertain to physically locating or measuring cable depth. Understanding the specific functionality of these devices clarifies why the electromagnetic detector is best suited for indicating the depth of a cable.