My intention is to explain each part of the system Hop mentions above.
The BCS controller is a device purchased from http://www.embeddedcontrolconcepts.com/
It is a small electronic box (see first photo below) that allows control of a brewery or really many other things, it was made for brewing but I could easily see it being used to monitor and control an aquarium for example.
The way you talk to this BCS is by using a browser to visit the web site built into the box. (see second photo below for a screen shot of the browser) This box is on your computer network. Set up correctly, you can even put it on the Internet so you can control it from anywhere in the world. Simply put, this box observes temperature and turns devices on and off based on your choices. You can click on buttons on the screen to turn things on and off OR you can program the site to do things for you automatically.
As examples of what you can do with it:
Turn on or off refrigerators, pumps, electric heat elements, electric valves or any other device you can control with electricity.
The BCS will not control a brewery out of the box. It requires a bit more work to get it to do its' thing. The box is run on low voltage and it has ports to connect up to 4 thermal probes and it also has 6 control voltages to turn on and off Solid State Relays (SSR) (see third photo).
You have to purchase Solid State Relays which are simple devices which have four places to attach wires. The two upper posts are where you attach the hot wire, 120-230 volts (depending on which SSR you purchase), the bottom post are for the low voltage output from the BCS. When the BCS turns on the low voltage, the SSR turns on or connects, the 120v (or 230v)switch.
I put the BCS in a box and mount the SSRs in it as well. (See fourth and fifth photos below). In the fifth photo you can see the side of the box where I have mounted three receptacles. These are under the control of the BCS.
These outlets are only on when the BCS turns them on. Each is controlled by a separate SSR although two of them are turned on and off by the same 5v line from the BCS. This is because I want two of them to turn on at the same time to heat my HTL. The left duplex receptacle is controlled by one SSR. I have two 20A circuits there. I control two heat elements (mentioned above) that are mounted in my hot water tank (hot Liquor tank) (HTL). I use the left duplex receptacle for the pump that I run to recirculate the water in the HTL.
There is an iPhone app for the BCS that Noah Paci (club member here. Last two photos are screen shots) wrote. If you think about what I've said so far, I can control my HTL from my home (my brewery is a few miles away from my home). If I've pre filled the HTL and plugged it in. The BCS via the iPhone app allows me to turn on or off and/or adjust the temperature. If I'm going to brew, I can get the water heating while still home eating breakfast.
I currently use the BCS to control my HTL and will use it to control the heat tube device.