From what I remember from my old mechanical tty days
of 25+ years ago, ZCZC at the beginning and NNNN at the
end controlled the autostop. The first ZCZC told your TTY
to wake up - it was usually followed by a few seconds of
diddle to let machines get up to speed. While your machine
was receiving traffic the autostop did nothing and the machine
stayed up and running. If, after the last NNNN there was no
traffic, then it would turn the TTY off. Lots better than
letting it run all the time. Quieter too.
The NWS still uses ZCZC/NNNN. I think now it's just
tradition, unless there really ARE still a few model 28's
lurking around out there somewhere.
Tom NU4G
Where does the text "NNNN" originate (radio history) in text messages
below the "signature" line? I see NNNN used sometimes, depending on
the
particular NWS forecaster, with the National Weather Service text
messages about active tropical storms/hurricanes (which I might add,
seem to be frequenting my area lately HI). Also there is sometimes
the
"$$" being used along with the "NNNN"
