30-second sequences, where one station transmits for 30 seconds and then receives for the following 30 seconds 

15-second sequences, where one station transmits for 15 seconds and then receives for the following 15 seconds

One-minute sequences, where one station transmits for one minute and then receives for the following one minute

Two-minute sequences, where one station transmits for a full two minutes and then receives for the following two minutes



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