2-30. Assume that you are operating a radio station under listening silence and you receive a
message addressed to your call sign. The message directs you to change your operating
frequency. You will change frequency ONLY if you receive the correct ________________
(2-30. Answer: authentication digraph)
2-31. If you are transmitting a message, you should not require a station to break an imposed
radio ________________ for the sole purpose of accomplishing ________________.
(2-31. Answer: silence, authentication)
2-32. Radio Station W6T received a call from someone who identified himself as the operator at
Station R7I. The caller requested a communications check and asked what time the helicopters
were departing in the morning. The answer was: "0730." But then the W6T operator found he
had made a mistake and called R7I to say so. The R7I operator had not been on the air all night,
and he had made no such request.
Voice recognition must not be relied upon as a substitute for ________________.
(2-32. Answer: authentication)