How to let user know that an automatic process in a mobile app can still be triggered from a different screen?

I'm working on a mobile app with Bluetooth Low Energy, that can trigger some hardware by either holding the phone near it (primary action) or trigger the hardware manually by looking for nearby devices and showing them in a list (secondary action).

My 2 screens basically looks like this:

The main tab (Scan) is a simple animation showing the user to hold his phone near the device to trigger it. It will show another animation if it detects a device nearby a phone and sends a signal to trigger it.

The secondary tab (Manual) will show all nearby hardware that can be triggered manually (if applicable). The user can click on the circle to trigger the device.

Now, even if the user is in the "manual" subtab, he can still trigger a device by holding his phone next to the hardware device. But it might look that the user HAS to be in the "SCAN" tab for that to work. This might lead to a case where the user accidentally triggers because he thought that it would not work.

How do i make clear that the SCAN is still active, even if in the other tab. By extension, the trigger can even work if the user is in the application settings, or has the app running in the background.