The Vortex-R Series is a line of electronic sirens produced by Whelen Engineering. They are essentially 4000-series siren heads with Type-1 control cabinets that lack voice capability much like the Omni-Alert series. The Vortex-R Series contains a rectangular rotator unlike the square rotator in the 4004. Unlike the 4000 Series, one- and two-driver models were offered. Older models have a large fin mounted on the rear of the driver assembly, a trait inherited from the 4000 series.