Two hours later an alarm bell went off on the ELF radio in the sub’s communications room. Like all nuclear submarines, the Dallas was trailing a lengthy wire antenna attuned to the extremely low-frequency transmitter in the central United States. The channel had a frustratingly narrow data band width. Unlike a TV channel, which transmitted thousands of bits of data per frame, thirty frames per second, the ELF radio passed on data slowly, about one character every thirty seconds. The duty radioman waited patiently while the information was recorded on tape. When the message was finished, he ran
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