If your devices connected via Control Bus are automatically switching off at the same time, this is likely due to the Automatic Power Down (APD) feature.
A Control Bus connection will allow your devices to switch on and off in sync. The APD feature will automatically switch a device off after a selected period of inactivity.
Example:
With a CXC, CXA81, and CXN100 connected via Control Bus:
If you're playing from the CXC and then switch to using the CXN100, the CXC will eventually power down automatically after its set period of inactivity (APD triggers).
Because of the Control Bus connection, when the CXC switches off, it will also turn off the other connected CX devices - even if they’re still in use.
If you'd like to stop this from happening, you can do so by disabling the APD feature on the devices.
Please note that this will mean the devices no longer switch off automatically, so you will need to manually switch them off when they're no longer in use.