If your Philips baby monitor parent unit beeps and permanently shows a red screen it might have lost its connection to the baby unit. Follow the instructions below to reconnect your baby unit to the parent unit:
1) Remove the battery from the parent unit
2) Remove the batteries from the baby unit
3) Plug in the adapter of the parent unit and the baby unit
The next 4 steps (step 4 to step 7) are also explained in the video below.