The Walchem WPH410-54NU controller is now obsolete and the closest equivalent is the WPH600 controller. The new WPH600 series has upgraded features; for reference, here is the description of the old model:
pH/ORP controller, on/off control outputs, hardwired, cable glands, single isolated analog (4-20 mA) output, none, integrated datalogging and config file import/export via USB flash stick.
