The original post: /r/todayilearned by /u/Retrospectrenet on 2024-10-06 01:48:56.

Original Title: TIL police radio codes like 10-4 for affirmative all start with 10 to allow time for the radio to power up. The first syllable spoken of a transmission was often not understood due to early technology quirks. Officers were trained to wait after pressing the receiver but forgot when rushed.