Thanks for the info - all I know is that it seemed very irritating - I would much rather have a human hand pulling the lever back when needed. Over the years I have maintained that a warning signal used too often and when not really needed, negates the warning. People begin to "tune it out." I once lived in an apartment two stories over a firehouse in downtown Chicago - at all times of day and night (I was a third-trick train dispatcher with ICRR) they would leave the firehouse with sirens blaring - soon I became used to it and never heard them afterwards. I maintain that any warning signal used to extremes loses its effectiveness.
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