Which class of circuit is not capable of transmitting an alarm beyond the location of a single open or non-simultaneous single ground fault?

• A. Class A circuit
• B. Class B circuit
• C. Conventional detector
• D. Dry-type transformer

Answer: (B)

This question tests fault tolerance in alarm signaling loops. In a Class A circuit, the loop is arranged with redundant paths so signals can reach the panel even if part of the wiring opens or there is a single ground fault. That means an alarm can still be transmitted beyond the location of the fault. A Class B circuit uses a single, non-redundant path; a single open or a single ground fault can interrupt the circuit and prevent alarms from reaching the panel, so it cannot transmit beyond the fault location. The other options don’t describe a circuit topology: a conventional detector is a type of sensor, not a circuit class, and a dry-type transformer is a power component, not a signaling circuit class.