Building Automation Level II Practice Exam 2026 - Free Building Automation Practice Questions and Study Guide

Supervising a closed loop circuit requires knowing the exact electrical signature of a healthy loop and detecting any change to it. Placing end-of-line resistors at both ends creates a defined impedance when the loop is intact. The supervising device continuously reads that impedance, so if any fault occurs—such as a break, a short, or removal of a device anywhere along the loop—the impedance changes and a fault is detected. This double end-of-line resistor setup provides reliable, comprehensive monitoring of the entire loop, which is why it’s the common configuration for supervising a closed loop.

Using a single end-of-line resistor wouldn’t monitor the entire path as robustly; an open or short in parts of the loop might not be correctly detected or would be harder to localize. An open loop circuit isn’t suitable for supervision because there’s no closed path to carry a monitored signal. Voice verification is unrelated to circuit supervision.