E3 allows communication with data acquisition devices, controllers, PLCs (Programmable Logic Controllers), RTUs (Remote Terminal Units), or any another type of device, by using I/O Drivers or OPC Servers, according to the type of device or communication needed. I/O Drivers and OPC Servers work in this case as servers providing variables, that is, they provide information from the external world to E3, so that process supervising can be performed. Variables involved in this process are known as Tags and there are several types of Tags, according to their intended usage. In E3, two types of Drivers can be inserted, I/O Drivers (.dll files) and OPC Drivers.