What is a Class A circuit?

• A. Circuit capable of transmitting an alarm signal during a single open or non-simultaneous single ground fault.
• B. Circuit not capable of transmitting an alarm beyond the location of a single open fault.
• C. Transmits alarm by code (by device not circuit)
• D. Transmits alarm by increasing current on the circuit

Answer: (A)

Class A circuits are built so that a single fault won’t stop an alarm signal from reaching the panel. If a section of the loop opens or a single ground fault occurs at one point, the circuit still has a path to transmit the alarm, so the panel can receive it. This fault-tolerant behavior is what distinguishes Class A from other configurations. In contrast, a layout that cannot transmit beyond the fault would be a more limited setup (Class B). The other choices describe signaling methods rather than how the circuit handles faults.