In typical burglar alarm wiring, which device commonly requires the largest conductor cross-section?

• A. Sensor
• B. Control Panel
• C. Keypad
• D. Siren

Answer: (D)

The main concept here is that conductor size is driven by current draw. The device that needs the largest cross-section is the siren because, when an alarm sounds, it becomes an active load that draws a relatively high current to power the horn. That peak current can be much larger than what the other components—like sensors, keypads, or even the control panel itself—need continuously, so the wiring to the siren must be thick enough to carry that current without causing excessive voltage drop or overheating.

Sensors and keypads are low-power devices; they operate with small currents in monitoring and signaling roles, so they don’t require large conductors. The control panel is mostly a low-power brain with signaling duties and doesn’t itself present the high current path that the siren does during an alarm. Even if the panel controls the siren through a relay, the circuit feeding the siren is the one that benefits from a larger conductor, since that path carries the surge when the alarm is active.

In practice, this means the wiring to the siren uses larger gauge conductors to ensure reliable operation and maintain sufficient voltage at the horn during alarm conditions, while the wiring to other components can be thinner due to their smaller current demands.