What must a GMDSS Radio Operator ensure before initiating a TELEX call?

Before initiating a TELEX call, it is crucial for a GMDSS Radio Operator to ensure that the required equipment is functioning properly. This is essential because the reliability of communication depends on well-maintained and operational equipment. If the equipment is malfunctioning, it could lead to unsuccessful transmissions or a complete inability to send and receive messages, which is particularly critical in emergency situations where effective communication can save lives.

While it is also important to consider aspects like the power supply or the orientation of the antenna, these factors come into play after confirming that all necessary equipment is operational. Ensuring that the equipment functions correctly is the foundational step in establishing any communication link, including a TELEX call.