Radio Jargon

I watched Aliens today. In the scene where the ship is dropping to the planet below, the pilot says over the radio, “In the pipe. Five by five.” I realized that despite having seen this film several times, I had no idea what she meant, other than some general notion of well-being. My curiosity was piqued, so I looked around online and discovered that by “in the pipe,” she meant the ship was following the correct course, and by “five by five,” she meant her radio transmission quality was perfect. It turns out that “five by five” is a phrase commonly used by radio stations to report each others’ transmission quality, where the first number (1-5, 5 being the best) is the signal strength and the second number is the signal clarity. I learned other interesting things, too. Police, firefighters, and other emergency responders use radio codes with “10-” prefixes (e.g. 10-20) because, due to the nature of radio, the first syllable of a transmission tends to be garbled. By prefixing everything you say with “ten,” it will be that useless prefix that’s garbled and not the actual code. Moreover, old radios needed a second to “warm up” before anything spoken into them would be transmitted. The “ten” prefix helped people who forgot this. Military personnel obviously use procedure words like “over” and “out” to keep transmissions short. It can sound pretty cool, professional-like. You hear soldier characters in movies and TV shows say these things all the time, even when not transmitting over radio. It turns out that these words are only used for radio transmissions, and not when speaking in person. Some procedure words like “affirmative” and “negative” are designed to have multiple syllables so that the meaning is clear if one of the syllables is garbled, although the U.S. Navy is phasing out these two in particular because their last two syllables are the same. “Over and out” is never proper because “over” and “out” are mutually exclusive; “over” requires a response, and “out” does not.