Which device is a conventional detector?

• A. Transmits the alarm by code (by device not circuit)
• B. Transmits the alarm by decreasing current on the circuit
• C. Transmits the alarm by code (by device not circuit)
• D. Transmits the alarm by increasing current on the circuit (by circuit not device)

Answer: (D)

In a conventional detector, the alarm signal travels through the circuit itself rather than being sent as a coded message from the device. The panel monitors the current on each zone, and when a detector triggers, the circuit’s state changes in a way that typically draws more current (the device alters the circuit impedance or closes a contact). The panel then interprets that change as an alarm for that zone. This is different from systems where devices actively transmit a coded signal or address. So the best way to describe it is that the alarm is conveyed by the circuit current changing—increasing—rather than by the device sending a code.