The Walchem WCT400-542U controller is now obsolete and the closest equivalent is the WCT600 controller. The new WCT600 series has upgraded features; for reference, here is the description of the old model:
Cooling tower controller – bleed & feed, hardwired, cable glands, isolated 4-20 mA output, graphite electrode & flow switch manifold mounted on pp panel, 5 ft cable, integrated datalogging and config file import/export via USB flash stick.