A Zigbee switch and a Z-Wave sensor are fitted a few centimetres apart on the same wall. Why can the switch not act on the sensor directly?

A protocol is more than a radio band: it sets how devices join, how messages are built and passed on, and how they are secured. Two devices on different protocols cannot understand each other without a hub with both radios or a bridge in the middle. Being close together does not matter, and the way each is powered has nothing to do with whether they share a language.

They are too close together, so their signals cancel each other out

Only one of them can be mains powered on the same lighting circuit

Their protocols set different rules for joining and messages

The sensor must be paired to the switch over Bluetooth LE beforehand

Which band in a UK home is used by Wi-Fi but not by Bluetooth, Thread or Z-Wave?

The 5 GHz band (and 6 GHz) is Wi-Fi only. 2.4 GHz is tempting because Wi-Fi uses it, but Bluetooth and Thread share it too. 868–869 MHz is where European Z-Wave works, and 908–920 MHz is the North American Z-Wave band.

A customer asks why their sub-GHz door sensor sends a short burst and then goes quiet, instead of reporting all the time. Which explanation is accurate?

Many Ofcom IR 2030 entries set a duty cycle: the share of time a transmitter may be on. That is one reason a sub-GHz sensor reports briefly and goes quiet, and it also saves battery. The sensor is not faulty, it does not hop to another band, and it reports events itself rather than waiting to be asked.

Sub-GHz radios can only send messages when the hub asks for them

The sensor is faulty, as sub-GHz devices should transmit constantly

The quiet periods let the sensor change band to avoid 2.4 GHz traffic

Many IR 2030 entries limit how much of the time a transmitter is on

Free mock exam

Protocols and radio — Smart Home Technology Practice

Free topic-focused mock exam: all 30 questions on Protocols and radio, drawn from the wider Smart Home Technology bank. 35-minute timer, 70% to pass, worked explanation on every question. Use this when you've taken the full mock once and want to drill the topics you got wrong.

Questions: 30
Time limit: 35 min
Pass mark: 70% · 21/30
Question bank: 30

Free, no sign-up. Retake as many times as you like — the questions are reshuffled, with the answer order changed.

Sample questions

01A Zigbee switch and a Z-Wave sensor are fitted a few centimetres apart on the same wall. Why can the switch not act on the sensor directly?
- ATheir protocols set different rules for joining and messages
- BThe sensor must be paired to the switch over Bluetooth LE beforehand
- COnly one of them can be mains powered on the same lighting circuit
- DThey are too close together, so their signals cancel each other out
Why: A protocol is more than a radio band: it sets how devices join, how messages are built and passed on, and how they are secured. Two devices on different protocols cannot understand each other without a hub with both radios or a bridge in the middle. Being close together does not matter, and the way each is powered has nothing to do with whether they share a language.
02Which band in a UK home is used by Wi-Fi but not by Bluetooth, Thread or Z-Wave?
- A5 GHz
- B908–920 MHz
- C868–869 MHz
- D2.4 GHz
Why: The 5 GHz band (and 6 GHz) is Wi-Fi only. 2.4 GHz is tempting because Wi-Fi uses it, but Bluetooth and Thread share it too. 868–869 MHz is where European Z-Wave works, and 908–920 MHz is the North American Z-Wave band.
03A customer asks why their sub-GHz door sensor sends a short burst and then goes quiet, instead of reporting all the time. Which explanation is accurate?
- AMany IR 2030 entries limit how much of the time a transmitter is on
- BSub-GHz radios can only send messages when the hub asks for them
- CThe quiet periods let the sensor change band to avoid 2.4 GHz traffic
- DThe sensor is faulty, as sub-GHz devices should transmit constantly
Why: Many Ofcom IR 2030 entries set a duty cycle: the share of time a transmitter may be on. That is one reason a sub-GHz sensor reports briefly and goes quiet, and it also saves battery. The sensor is not faulty, it does not hop to another band, and it reports events itself rather than waiting to be asked.

Common questions

Is the Protocols and radio mock exam free?

Yes — 100% free, no sign-up needed. Questions are pulled at random from a substantial bank, with a worked explanation on every question after you submit.

Can I retake the mock exam?

Yes. Every attempt picks a different random selection and reshuffles the options, so each retake gives you genuinely new questions. No limit on retakes.

Does this count towards the real qualification?

No — this is independent practice material. To gain the actual qualification you need to sit the official assessment through an approved provider.