Abstract text

A shut down unit for use with an electro-pneumatic controller includes an electronic switch configured to receive to a first signal from a control unit of the electro-pneumatic controller and to convey the first signal to an electro-pneumatic transducer of the electro-pneumatic controller. The electronic switch is further configured to receive a second signal associated with a control signal input and to cause the electronic switch to prevent the conveyance of the first signal to the electro-pneumatic transducer.