"Well, to begin ... I'm pulling up some of this on my computer ... okay, ELF waves are transmitted at extremely low frequencies ..." He chuckled to himself and said, "That's why they're called ... Anyway, these are extremely long waves, so say you're transmitting at 82 herz, or 0.000082 megaherz-that's equal to a wavelength of 3,658,535.5 meters, or 3,658.5 kilometers-"

I dropped my pencil and said, "Hold on, John. Hold on. We don't want to send a message on our ELF transmitter. Who uses this wavelength? And what's it used for?"

He replied, "It's only used by the military. Specifically, the Navy. It's used to contact nuclear submarines operating at very low depths."

Kate and I looked at each other. I wanted to ask him if he knew Fred, but instead I inquired, "Can these ELF waves be monitored?"

"Sure. If you have the right equipment. But you might wait a long time to hear an ELF transmission."

"Why?"

"They have very limited use. And anything you heard would be encrypted."

"Okay ... take us through this. Who, what, where, when, how, and why?"

"I don't think anything I'm going to say is classified, but I need to ask you if you're on a secure line."

Typical military commo guy. I thought maybe Ned was listening to pass the time of day, but he didn't look like a spy, and Wilma was probably watching the Home Shopping Network. I said to Commander Nasseff, "We're on a regular landline, and it's a one-time use for me at a resort up in the Adirondacks." We weren't actually in the Adirondack Mountains any longer, but that's where Walsh and Griffith needed to think we were if this conversation got back to them. I added, "A resort called The Point. The chef is French, but I'm sure he's not listening in."

"All right ... as I said, most of this is not classified. So let me explain the practical application of ELF technology. As you know, we have nuclear subs operating at very low depths for extended periods of time-months, sometimes-and most of these subs operate in their regular patrol areas near ... well, this is a little sensitive, but I'll say near underwater hydro-acoustic stations where they can be in touch with naval operations through normal radio channels. But some of these subs can be out in no-man's-land, too far from these underwater stations, so in an emergency situation, naval operations in Pearl Harbor, for the Pacific Fleet, or Norfolk, for the Atlantic Fleet, need to get in touch with these nuclear submarines that are not near the surface or near an underwater relay station. Follow so far?"

I looked at Kate, who nodded, and I said, "Sure. Go on."

"Well," he continued, "as a for instance, normally used VLF waves-very low frequency-won't penetrate deep into the ocean depths, especially if the water is very saline. Salty."

"I got salty."

"Good. But ELF waves can travel all the way around the world regardless of atmospheric conditions, and they can penetrate anything, including mountains, oceans, and polar ice caps. They can reach a deeply submerged submarine anytime, anyplace. In fact, if it weren't for the existence of ELF waves, we'd have no communication with some of these vessels in our nuclear submarine fleet, and that could lead to a major problem if the balloon went up."

"What balloon?"

"The balloon. That's slang for atomic war."

"Right. I like balloon better." Again, Kate and I looked at each other, trying to comprehend this. I didn't know how she was feeling, but thinking of Bain Madox, I was a little worried.

Commander Nasseff made a funny doomsday joke by saying, "If it wasn't for ELF, we couldn't have a good, all-out atomic war."

"Well, thank God for ELF."

He chuckled. "That's an old Navy commo joke."

"That's a real knee-slapper. Got any more?"

"Well, gee, it's been a long time since the Cold War, but-"

I interrupted. "So, that's the only way ... the only reason anyone would use an ELF radio-to talk to a submarine."

He replied, "Well, it's not actually a voice radio-it's more of a signal transmitter-like a telegraph-to send encrypted letter-code messages."

"And only to a submarine?"

"Right. A deeply submerged submarine. ELF waves are very long, and therefore the transmissions are very slow. But they can penetrate anything. Thus, their only practical use is to contact submerged submarines that can't be contacted by normal means."

"Right. Can ELF waves screw up my cell phone?"

He chuckled again. "No. These waves are so far off the chart, they wouldn't interfere with any other radio waves, microwaves, or anything we currently use on a day-to-day basis."

Kate said to him, "So, these ELF transmissions are letter codes."

"Correct."

"And they can only be picked up by submarines?"

"Well, they can be picked up by anyone with an ELF receiver. But unless you know the code, which changes often, it would be meaningless. All you'd hear would be transmitted pulses, which are the letters in encrypted form. From what I understand, a three-letter code is the most common."

Kate asked, "And that tells the people on the sub everything they need to know?"

"Usually, it just tells them that they need to establish normal radio communication." He explained, "An ELF transmission is called a bell ringer. It's to alert a submarine commander that a situation is developing, and he needs to do something to get in touch. But sometimes the three-letter code is self-explanatory. For instance, it could mean 'Surface' or 'Proceed to location A,' which is a predesignated grid coordinate. Follow?"

Kate replied, "I think so."

"You can't use ELF for long, chatty messages. It can take half an hour for the signal to reach the sub. And I should point out that the submarine can't send an ELF signal or message. It can only receive one."

I said, "Like, 'Don't call us, we'll call you.'"

"Correct."

Kate asked, "Why can't a sub send an ELF message?"

"The transmitter and antenna need to be on land. I can explain that later. But meanwhile, if a submarine needs to reply to this one-way message, or if the sub commander needs more data, then the sub would need to get near an underwater hydro-acoustic station-if there's time-or would need to get near the surface and send up a communication buoy to reply or get more information via VLF, or these days via satellite, or other means."

I inquired, "What do you mean, 'If there's time'?"

"Well, for instance, if the other side has already launched ICBMs against us, then there's no time to establish normal radio communication, because by the time the sub receives an ELF signal, which, as I said, can take thirty minutes, all forms of communication in the U.S. have already been vaporized, and the atomic war is all but over." He explained, "If that's what's happening on the surface, then the submarines receive the last and only ELF message they will ever get-a three-letter code that means ... well, 'Fire away.'"

Kate looked a bit worried, but Commander Nasseff had good news. "ELF waves are not affected by thermonuclear explosions."

I said, "Thank God for that. But let me ask you-what if the guy sending the atomic-launch code sends the wrong letters? Like, he means to type in XYZ, which means 'lunch break,' but he screws up and types in XYV, which means 'Launch your nukes'?"

Commander Nasseff replied with a little amusement in his voice, "That can't happen."

"Why not? Look at the e-mails you get."

"I mean," he explained patiently, "there are safeguards, and all orders to launch need to be verified."

"By who? By the time the sub gets the order a half hour after it's sent, as you just said, there's no one left to verify anything."

"This is true. But rest assured that can't happen."