Which detector transmits the alarm by code rather than by altering circuit current?

• A. Conventional detector
• B. Dry-type transformer
• C. Conventional-addressable detector
• D. Analog-addressable detector

Answer: (C)

The key idea is that some detectors communicate alarms with a coded signal that includes a device address, rather than simply changing the current on the circuit. Conventional detectors only cause a fault by altering the loop current, so the panel knows a zone is active but can’t identify which device within that zone. Addressable detectors, on the other hand, send a digital code that identifies the specific device and its status. Among the choices, the conventional-addressable detector fits this description best because it operates on a conventional system but still transmits alarm information as a coded signal with an address, allowing the panel to pinpoint the device. Dry-type transformer isn’t a detector, and while analog-addressable detectors also use coded signaling, the option describing a detector with addressing on a conventional system is the intended match here.