The exchange went basically as follows: "Any unit FCC". The field unit would give their call sign and say, "KA 4306". The dispatcher would usually respond, "10-4 Thank you. KMA 628" and then give the time. The "KMA" prefix was a law enforcement designation and the numbers distinguished the agency. For example, LAPD was KMA 367 and LASD was KMA 628. More @Wikipedia
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