You only need internet connection for setting up screen for first time and updating content.
Once content is synchronized, you all campaign you have published to your displays will be visible even if the device loses connection.
Note there are a few tools available only when device is online:
- Live remote view;
- Remote control, reboot or shut down device;
- Triggering campaign on demand;
- Updating OnSign TV app version.
At last, you can even update your campaigns on offline players with an USB stick (check out tutorial).