G&B Specialties’ Model 856 switch circuit controller provides reliable positive electrical detection of the position of rail switch points. Model 856 controllers can also detect the position of derails, bridge locks and slide detectors. Additionally, they are capable of controlling relay circuits or shunting track circuits. The Model 856 switch circuit controller is available in a four-way configuration for two-position, three-position and polarized applications. A two-position controller may be used without change of parts for polarized application by proper cam and circuit adjustments. A two-position controller may also be used as a three-position controller for two circuits by using two cam spaces for each three-position circuit and the proper cam adjustments. A three-position controller for four circuits is obtained by substituting combined three-position cams, in place of a two-position cam and the substitution of the camshaft. The terminals, contacts, operating cams and other components are installed in a rugged cast iron weatherproof housing. A hinged cast iron cover (aluminum also available) provides easy access to the interior for inspection, adjustment and maintenance of parts.