'Warning piece' definitions:

Definition of 'Warning piece'

From: GCIDE

Warning \Warn"ing\, a. Giving previous notice; cautioning; admonishing; as, a warning voice. [1913 Webster]
That warning timepiece never ceased. --Longfellow. [1913 Webster]
Warning piece, Warning wheel (Horol.), a piece or wheel which produces a sound shortly before the clock strikes. [1913 Webster]