Crestron Tutorial: Crestron SIMPL Windows Control Symbols Versus Signals
Unfortunately, this tutorial has to get dry at some point. Well, here it is... Crestron programming employs things called Symbols and Signals.
Symbols are graphical representations of devices or functions. That is, a Crestron symbol could represent anything from a simple AND gate to a complex set of functions for an LCD Projector. These symbols are grouped into the categories of Analog, Digital and Serial. Special manufacturer authored symbols are available for certain products.
Signals are used as paths between Symbols. Imagine them like wires from one contact on an integrated chip to another contact on another chip. You create Signals by entering text at the appropriate place on a Symbol. Signals cannot contain empty spaces so if you type a space, then SIMPL Windows will enter an underscore for you.
While Crestnet is not related to either symbols or signals, I thought that I'd explain it a little here. Crestnet is a four wire communication wiring. Two wires are DC power and the other two are communications. It is essentially RS422 that can run further. I think it can run up to 5000 feet or so.