Where are ferrite beads commonly placed in an alarm system?

• A. On the main breaker
• B. On detector leads and incoming power
• C. At the transformer secondary
• D. Inside the panel cabinet

Answer: (B)

Ferrite beads act as high‑frequency noise suppressors, soaking up RF interference on cables. In an alarm system, you want to keep the lines that carry detector signals and the power entering the control panel free from high‑frequency noise, because EMI can cause nuisance alarms or unreliable reads. Placing ferrite beads on detector leads and on the incoming power minimizes interference where it’s most likely to enter the system, making this the most effective location. They aren’t typically used on the main breaker, the transformer secondary, or tucked inside the panel cabinet for this purpose, since those spots don’t address noise on the signal and supply lines as directly.