Etymology of 10-20

From a citizens' band radio reinterpretation of "10-20" from the 1940 ten-codes devised by the Association of Public-Safety Communications Officials-International (APCO), which in turn was based on an unnamed standard invented by Charles "Charlie" Hopper for the Illinois District 10 State Police in 1937 that subsequently spread to the rest of Illinois, Iowa, Missouri, and Minnesota and was documented by APCO in 1939. The syllable "ten" was originally chosen to help novice operators fill an appropriate amount of time so that the dynamotor used to power 1930s and 1940s radio transmitters could spin up to full power before the semantically meaningful second number was transmitted. These second numbers were assigned with the aim that more useful common messages would be given smaller numbers, and similar messages would be roughly grouped into "brackets". The message "what is your location?" was placed in a 13–20 squad-car management bracket by the 1940 committee as one of its stated goals was to move these meanings to lowest of the situational numbers, but the reason for its placement at the end is not recorded. Its meaning subsequently generalized from the specific question to just "location" with the advent of CB radio.

{
  "templates": [],
  "links": [
    [
      "citizens' band radio",
      "citizens' band radio"
    ],
    [
      "ten-codes",
      "ten-code"
    ],
    [
      "dynamotor",
      "dynamotor"
    ]
  ],
  "references": [],
  "descendants": [],
  "lexical": [
    {
      "pos": "noun",
      "glosses": [
        "Location."
      ],
      "tags": [],
      "recordId": "4e99ee4613fdd5ad0eb53dedeaef5b22fbc0543a5722e4a99f2fadf9d4297ebd",
      "rawRecordSha256": "ef97f7c359718f823c17e54aab85fd673867b70a2e36d0a0aa30e16f3d1fc240",
      "sourceRecordOrdinal": 246627
    }
  ],
  "omittedAuxiliaryFields": {
    "templates": 0,
    "links": 0,
    "references": 0,
    "descendants": 0,
    "lexicalRecords": 0,
    "lexicalSenses": 0,
    "glosses": 0
  }
}