The Walchem WNI 400 series controller is now obsolete and is replaced by the WNI6 series controller. The new series has upgraded features; for reference, here is the description of the old model:
Nickel Controller
Control: 4 control relays and calibration reminder
Output: 4-20mA
Nickel Plating Controller for electroless applications. With four control relays, calibration reminder, optional analog outputs, nickel sensor only or nickel and pH sensor inputs.