What happens to the Portable People Meter if it detects no motion after 20 minutes?

When the Portable People Meter detects no motion after 20 minutes, the green light goes off as a signal to the user. This feature is important because it indicates that the device is no longer actively tracking the user's movements. The green light serves not only as a visible indicator of the device's active state but also helps ensure that users are aware of its proper functioning. The absence of motion prompts the device to enter a standby or inactive mode, conserving battery life and maintaining data integrity for the moments when it is used. This functionality is crucial for effective data collection in audience measurement contexts, allowing for more accurate tracking of user interactions with media.