Has the meaning given to that expression in the SMETS1 Supporting Requirements.
For a SMETS1 Alert, shall mean the SMETS1 Mandated Event Message Code or the SMETS1 Non-Mandated Event
Message Code. For a SMETS1 Response, shall mean the value of GBCSHexadecimalMessageCode (with its Message
Mapping Catalogue meaning) required by Clause 9.