For me it’s the notification light you used to find on older phones, was particularly good to know if your phone was charged without picking it up

    • MrsDoyle@lemmy.world
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      9 months ago

      It was a build-up of something or other (carbon?) on the microphone part of the caller’s handset. You could fix it by tapping the handset sharply on a hard surface. Source: I used to work in radio back in the 80s.