I worked Supervisory Control & Data Acquisition systems for water treatment for 8 years and the electric utility company for 2 years.
As kellys_eye said, most industrial process control instrumentation runs 1-5V/4-20mA. The SCADA system is the central computer system that monitors all those process control devices.
If you're unfamiliar with 4-20mA current loops, you're going to have to learn them quick.
If you're going to take this job, ask them the manufacturer and model number of their SCADA computer system so you can study-up on it before you start there so you don't look like you're not competent in it.
All the 4-20mA system devices use feedback to read and adjust plant processes (open/close (or anywhere in between) valves, pressures, water and pneumatic levels, differential potentials for level controls, and whatever else they're using). They're specifically asking for a 'SCADA' tech because they want somebody who knows how to interface all those 4-20mA devices to THEIR COMPUTER SYSTEM.
I'd ask whoever you talked to, to identify specifically that computer system so you don't walk into this job empty-headed. The employer might give you access to their documentation, but you sure as heck can look it up on-line and familiarize yourself with what they've got before you get there.
Also ask them if they're using signal wire or fiber optics (or wireless) to interface their equipment with the SCADA system so you know what they've got before you get there.
Good luck. The pay is usually good, but you're going to get call-outs in the middle of the night when critical systems hang-up.
If the salary is right, you may not care about the ins and outs.
