There are two methods to request the retransmission of a message. These methods are

There are two methods to request the retransmission of a message. These methods are

• A. a service message
• B. operating signals
• C. both a service message and operating signals
• D. neither

Answer: (C)

When you need a message resent, you have two mechanisms to request retransmission: a service message and operating signals. A service message is a formal, structured request within the messaging system that explicitly asks for the previously sent data to be resent, usually including identifiers like the message ID or sequence number to ensure the correct item is retransmitted. Operating signals are quick, prearranged cues used by the operators themselves to indicate a need for retransmission, which can be faster or necessary when the channel conditions prevent sending a formal message. Using both options gives flexibility: the service message provides a clear, trackable record of the retransmission request, while operating signals allow rapid action when time or channel constraints make a full service message impractical. Because reliability depends on being able to recover lost or garbled data in different situations, both methods are valid and commonly used.

When you need a message resent, you have two mechanisms to request retransmission: a service message and operating signals. A service message is a formal, structured request within the messaging system that explicitly asks for the previously sent data to be resent, usually including identifiers like the message ID or sequence number to ensure the correct item is retransmitted. Operating signals are quick, prearranged cues used by the operators themselves to indicate a need for retransmission, which can be faster or necessary when the channel conditions prevent sending a formal message. Using both options gives flexibility: the service message provides a clear, trackable record of the retransmission request, while operating signals allow rapid action when time or channel constraints make a full service message impractical. Because reliability depends on being able to recover lost or garbled data in different situations, both methods are valid and commonly used.