A heavy-duty (aluminium alloy) switch box contains a pair of contact micro switches activated by two cams on a shaft driven by the actuator. These signal the full open and closed valve position. Both switches are independently adjustable and terminals are provided for the systems' connection. The switch box is of generous proportions and has two electrical entries so that, with additional terminals, the connection to the actuators' HD switch boxes can be supplied to a waterproof specification, IP 67 to IEC 529, or explosion proof EEx d (European certification), or Class l div 1 group C, D. Class II div 1 group E, F, G. (CSA certification).