A molded case circuit interrupter comprising: a molded case comprising a first case portion and a second case portion, the molded case having an interior region formed therein that is situated between the first and second case portions (12, 16); an electrical apparatus situated on the molded case, the electrical apparatus comprising a set of separable electrical contacts situated within the interior region, a handle that is structured to at least initiate movement of the set of separable contacts between an OPEN condition and a CLOSED condition, and a circuitry component; the molded case having an exterior surface opposite the interior region, the exterior surface comprising a front exterior surface and a rear exterior surface that face in opposite directions away from one another, the handle being situated at the exterior of the molded case circuit interrupter adjacent the front exterior surface; characterised by an accessory (50, 52) situated in an accessory cavity (44, 46) within the interior region and being structured to perform an operation; the circuitry component comprising a substrate situated adjacent the rear exterior surface and further comprising a number of electronic components situated on the substrate, the number of electronic components being structured to provide a data processing capability that is electrically communicated to the accessory (50, 52); and the substrate comprising a number of electrical conductors and a support, the number of electrical conductors being situated on the support, the support being formed of an electrically insulative material, at least some of the electronic components of the number of electronic components being electrically connected with at least some of the electrical conductors of the number of electrical conductors. a molded case comprising a first case portion and a second case portion, the molded case having an interior region formed therein that is situated between the first and second case portions (12, 16); an electrical apparatus situated on the molded case, the electrical apparatus comprising a set of separable electrical contacts situated within the interior region, a handle that is structured to at least initiate movement of the set of separable contacts between an OPEN condition and a CLOSED condition, and a circuitry component; the molded case having an exterior surface opposite the interior region, the exterior surface comprising a front exterior surface and a rear exterior surface that face in opposite directions away from one another, the handle being situated at the exterior of the molded case circuit interrupter adjacent the front exterior surface; characterised by an accessory (50, 52) situated in an accessory cavity (44, 46) within the interior region and being structured to perform an operation; the circuitry component comprising a substrate situated adjacent the rear exterior surface and further comprising a number of electronic components situated on the substrate, the number of electronic components being structured to provide a data processing capability that is electrically communicated to the accessory (50, 52); and the substrate comprising a number of electrical conductors and a support, the number of electrical conductors being situated on the support, the support being formed of an electrically insulative material, at least some of the electronic components of the number of electronic components being electrically connected with at least some of the electrical conductors of the number of electrical conductors.