Where are ferrite beads installed for CE compliance?

• A. On the power cable coming from the control panel
• B. On the metallic keypad frame
• C. On the data cable coming from the control panel; bead is positioned inside the plastic keypad case
• D. On the siren cable

Answer: (C)

Ferrite beads damp high-frequency EMI on signal cables, which is a common source of emissions that CE compliance tests target. In an alarm system, the data cable from the control panel carries rapid digital transitions, so placing a ferrite bead on that cable directly reduces the high-frequency currents that could radiate from the path between the panel and the keypad. Positioning the bead inside the plastic keypad case helps keep the suppression right at the interface where the cable enters the device, ensuring the EMI is attenuated before it can contribute to emissions tested during CE certification, while avoiding interference with the power supply.

Using a bead on the power cable or on the metallic keypad frame isn’t as effective for addressing the primary EMI path between the control panel and keypad. A bead on the siren cable could help if that cable were a known source of high-frequency noise, but the standard approach for meeting CE requirements in this setup is to filter the data cable coming from the control panel, with the bead located inside the keypad case.