# If a subsystem (rotator, secondary/tertiary mirror, dome) loses comms with ServoSCommunicator, a (pinkish) red warning box will appear in that subsystem's GUI complaining of Bad Comms. The first fix to try is to navigate to the appropriate subsystem's tab in the ServoSCommunicator GUI and reselect the port from the dropdown list. The ports are as follows:
. * Rotators: /dev/ttyUSBRot2. * Secondary & tertiary mirrors: /dev/ttyUSBFoc3. * Dome: /dev/ttyUSBDom4
The most common issue is '''loss of dome comms'''. There is a watchdog on the dome that causes it to close after five minutes of bad comms - sometimes the warning message does not appear before the dome automatically closes. This problem isn't usually solved using the fix above and ServoSCommunicator will need to be restarted. If the SiTech software was started using the script, you'll need to close all the GUIs and start again. Otherwise you can leave SiTechExe running (you'd probably want to do this if the dome hasn't yet closed, and you want the telescope to keep tracking while the instrument is exposing) and close everything else: first close ObservatoryControl, then the rotator, focuser and dome GUIs, then ServoSCommunicator, and restart in the order given in [[#Starting SiTech software|Step 5b]].