Final answer:
Emergency calls should be given the highest priority, followed by Priority messages, and Routine communications which have the lowest priority for interphone transmissions.
Step-by-step explanation:
The correct priority for interphone transmissions is as follows: Emergency calls should be given the highest priority, followed by Priority messages, and lastly, Routine communications. Emergency communications are critical and must be addressed immediately to ensure safety and prompt response to potentially life-threatening situations. Priority messages are important, but they do not supersede emergency communications, while routine communications should be handled only after the more urgent messages have been dealt with.