The Sorteberg relay, or Sorteberg force bridge pneumatic relay is a form of analog pneumatic computer, calibrated to calculate a predefined function. They were sold by Sorteberg Controls Corp.
It consists of a series of bellows, joined by a beam. The balance of forces between the bellows across the beam is responsible for performing the computation. The end of the beam often controls a flapper nozzle, which itself provides a varying pressure input to a pneumatic relay. This output can then be directed to other components. The Sorteberg relay has seen use in process control in oil refineries and numerous other facilities.