Proper earth with < 0.5 ohm measured from the Com.X stud to the earthing point, preferably to telco or failing that, building earth should be present on all installations.
The Com.X provides an earth connection in its power brick and cable. If a good mains earth is present, a separate earth strap to the Com.X earth stud could be unnecessary.
The Comma iTA (if present) does not have an earth connection in its power brick and must be earthed using an earth strap and its earth stud.
It is important that Com.X and iTA devices are earthed in a “star” pattern to a single earthing point. Do not wire an iTA to a Com.X’s earth stud or vice versa.
Be careful not to create earth loops which may induce noise into the system. Ensure high quality multi-adapters (multi-plugs) are employed, and do not place the Com.X at the end of a chain of devices chained on the same multi-adapter.