The Walchem WDB400-1N5U controller is now obsolete and the closest equivalent is the WBL600 controller. The new WBL600 series has upgraded features; for reference, here is the description of the old model:
Dual boiler controller, 120 VAC, prewired, no 4-20 mA output, two standard electrodes (up to 250 psi), integrated datalogging and config file import/export via USB flash stick.
