Dwyer Series BB Differential Pressure Controls employ two Bourdon tubes and a Mercoid mercury switch to indicate a difference in pressure between two sources. Applications include indicating pressure drop across a strainer or screen, maintaining correct process flow relation, and indicating oil pressure failure in refrigeration equipment. The controls are available in various housings, including weather-proof and explosion-proof options, and have an electrical capacity of 5A @ 120V, 2A @ 240V AC, and 25A @ 120V, 1A @ 240V DC.