text: An additional use for the injector technology is in vacuum ejectors in continuous train braking systems, which were made compulsory in the UK by the Regulation of Railways Act 1889. A vacuum ejector uses steam pressure to draw air out of the vacuum pipe and reservoirs of continuous train brake. Steam locomotives, with a ready source of steam, found ejector technology ideal with its rugged simplicity and lack of moving parts. A steam locomotive usually has two ejectors: a large ejector for releasing the brakes when stationary and a small ejector for maintaining the vacuum against leaks. The exhaust from the ejectors is invariably directed to the smokebox, by which means it assists the blower in draughting the fire.  The small ejector is sometimes replaced by a reciprocating pump driven from the crosshead because this is more economical of steam and is only required to operate when the train is moving.
  Vacuum brakes have been superseded by air brakes in modern trains, which allow the use of smaller brake cylinders and/or higher braking force due to the greater difference from atmospheric pressure.