The Walchem WCT400-1N1U controller is now obsolete and the closest equivalent is the WCT600PSNNN-AN controller. The new WCT600 series has upgraded features; for reference, here is the description of the old model:
Cooling tower controller – bleed & feed, 120 VAC, prewired, no 4-20 mA output, graphite electrode & tee , 20 ft cable (for in-line or submersion mounting), integrated datalogging and config file import/export via usb flash stick.