LK portable dryer
That was a feature borrowed from the full-size machines called "Wrinkle Guard". On those, tumbling would stop and buzzer would sound. If door wasn't opened, dryer would start up again every 5 minutes, tumble for a while, then stop and buzz again. This would go on for hours, length of time depending on whether the machine had Wrinkle Guard I, II, or III. I use it when drying dress shirts and pants I wear to interviews.
"Best part of the dryer was the Permanent Press cycle. The buzzer would sound when the cycle was done, but it kept tumbling without heat (buzzing occasionally) until you actually turned it off. Sure wish my new Frigidaire had that!"