Inside the model gate
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A visitor could actuate the model gate by pressing a button that set its little opening mechanism in motion. An endogenous change occurred when a weight inside the defined mechanism shifted and altered the gate's balance without a change in the surrounding conditions. A faint rattle seemed to emanate from the small box beneath the model, drawing the builders' attention to that location. They paused the demonstration and traced each event before deciding which part needed adjustment.
The button still had to actuate the opening mechanism reliably, so the builders tested it separately from the balance problem. They traced the endogenous change to the internal weight and secured that part instead of changing the lighting or other outside conditions. When the rattle continued to emanate from the lower box, a loose cover provided a second, separate explanation. Recording the two findings prevented the team from treating every symptom as evidence of the same cause.
Before you move on
Look away from the passage. Can you explain each focus word in your own words?
Original fictional passages for vocabulary practice.