Final answer:
When the portable RAIC reader says 'unknown', the security guard should follow the established protocols and procedures.
Step-by-step explanation:
When the portable RAIC reader says "unknown", it means that the security guard does not have any information about the person or identification presented. This could happen if the person is not registered in the system or if there is a technical issue with the reader. In this situation, the security guard should follow the established protocols and procedures. They may ask the person for additional identification or contact their supervisor for further guidance.