The Walchem WDT400-5N1U controller is now obsolete and the closest equivalent is the WCT600HSSNN-AN controller. The new WCT600 series has upgraded features; for reference, here is the description of the old model:
Dual cooling tower controller, hardwired, cable glands, no 4-20 mA outputs, two graphite electrodes with tees (for in-line or submersion), 20 ft cables, integrated datalogging and config file import/export via usb flash stick.