The designation of a Signaling Line Circuit (SLC) style depends on which conditions?

• A. Fault tolerance during a single open, single ground, wire-to-wire short, and loss of carrier fault condition.
• B. Operator preference and local codes.
• C. The length of the run and insulation type.
• D. The presence of a backup power supply.

Answer: (A)

The thing being tested is how an SLC style is chosen based on how the signaling line circuit behaves when faults happen. An SLC is a supervised two-wire (or four-wire) path that carries data between the panel and devices, and its style tells you exactly what faults the circuit can tolerate without losing signaling and how those faults are reported. The designations reflect tolerance to several fault conditions: a single open in the pair, a ground fault on a conductor, a short between wires, and a loss of the carrier signal. These fault scenarios determine how devices on the loop communicate with the panel, when a fault is flagged as a trouble versus an alarm, and whether communication can continue despite faults. Operator preference, local codes, run length, insulation type, or the presence of backup power don’t set the SLC style—the style is defined by the circuit’s fault-tolerance characteristics described above.