The Walchem WPH410-541U 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, preamplifier (190783) w/10’ cable, pre-wired, integrated datalogging and config file import/export via USB flash stick.