Why is the automatic answerback request (WRU) first used by the LES after an Inmarsat-B TELEX call has been placed from a ship?

In the context of an Inmarsat-B TELEX call, the automatic answerback request (WRU) is utilized by the Land Earth Station (LES) primarily to identify the Specific Earth Station (SES) making the request. This identification is crucial as it allows the LES to recognize the particular ship's station that initiated the call and ensures that the communication is directed correctly to and from the intended sender.

Recognizing the SES helps in managing communications more efficiently, as the LES can promptly respond to incoming requests. This also aids in supervising the overall network and ensuring compliance with operational protocols. The identification process is fundamental in establishing a secure and orderly communication link, which is vital for effective maritime communication.

The other options, while they do touch on various aspects of communication protocols, do not directly address the primary function of the WRU in this context.