hard KNX Advanced exam questions

Hard level questions

1. Q01

   On highly sensitive KNX Secure installations (strategic sites, defence buildings), the keyring keys can be stored in a Hardware Security Module (HSM) attached to ETS, guaranteeing that the keys never leave the secure hardware even during download operations.

   TrueFalse

   X. KNX Secure· HSM (Hardware Security Module)· Hard

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   Correct answer

   True

   Learning tip

   An HSM is a certified hardware device (typically FIPS 140-2 level 3 or above) that stores cryptographic keys with several protections: true random key generation (TRNG), crypto operations executed in protected memory (the key is never in the clear in ETS RAM), tamper-evident audit logging and physical tamper detection. A USB HSM costs roughly 500-5000 euros and is reserved for high-security sites: banking, defence and critical infrastructure. It is standard practice in those sectors, exotic everywhere else.

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2. Q02

   What is the principle of Constant Light Control regulation in KNX?

   • A.Maintain a fixed illuminance (e.g. 500 lux) by varying the artificial lighting in response to the natural daylight contribution
   • B.Switch every lamp to full power as soon as a presence sensor detects occupancy
   • C.Dim linearly from 0 to 100% over the course of the day (sunrise to sunset)
   • D.Switch lighting off automatically after X minutes of inactivity

   5. Lighting Control· Constant Light Control· Hard

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   Correct answer

   A — Maintain a fixed illuminance (e.g. 500 lux) by varying the artificial lighting in response to the natural daylight contribution

   Learning tip

   (A) is correct: Constant Light Control is a closed-loop combination of a lux meter and a dimming actuator. The controller compares the measured illuminance to the setpoint (e.g. 500 lux) and adjusts the artificial output to cover the gap left by natural daylight from the windows. Energy savings are typically 30-60% versus simple on/off switching, and the function is usually paired with presence detection to avoid lighting unoccupied zones. (B) describes a brute-force presence-on-full strategy with no light regulation. (C) describes a time-based daylight curve, not closed-loop regulation. (D) describes an absence time-out, which is a separate function.

   Source: ABB i-bus KNX Lighting Application Manual (public)

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3. Q03

   The emergency lighting of a building CANNOT be driven by KNX alone: it must comply with dedicated standards (NF EN 1838, EN 50172) that require a self-contained system with a backup battery.

   TrueFalse

   5. Lighting Control· Sicherheitsbeleuchtung· Hard

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   Correct answer

   True

   Learning tip

   A self-contained emergency luminaire is a regulatory obligation: it has a local battery and operates without either mains supply or bus communication. KNX can supplement it with test/diagnostic functions or with the normal switching command (self-contained luminaires light up when the 230 V supply fails), but it must NEVER replace the autonomous emergency system. This is a classic exam topic for tertiary projects.

   Source: NF EN 1838 / EN 50172, ABB lighting AM

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