Fault Diagnosis Test
Twenty-four timed puzzles in the real technical-selection format — follow a signal through switches and processing units, trace values, and pinpoint the faulty component. We score you and email a section-by-section report with your percentile.
⏱ 25:00
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A signal enters on the left. Each unit applies its operation only when its switch is ON (OFF = passes straight through). What value comes out?
Fault diagnosis tests measure how logically and quickly you can find a fault in a system. You follow a signal through switches and processing units, work out what the output should be, and pinpoint the component that has failed. They're used to select for technical, maintenance and engineering roles — especially rail, aviation, the armed forces and manufacturing — where systematic fault-finding is the core of the job.
This free test mirrors that format: 24 timed puzzles across four areas. Each unit does one clear thing, so the puzzles reward methodical tracing over guesswork. We score every section and email you a breakdown with your percentile, so you can see where you're strong and where practice helps most.