The DCS is usually used in factories and located within a more confined area. It uses a high-speed communications medium, such as local area network (LAN).
DCS is process oriented: it looks at the controlled process as the center of the universe, and it presents data to operators as part of its job
In a DCS, the data acquisition and control functions are performed by a number of distributed microprocessor-based units situated near to the devices being controlled or the instrument from which data is being gathered.
DCS systems have evolved into systems providing very sophisticated analog control capability. A closely integrated set of operator interfaces (or man-machine interfaces) is provided to allow for easy system configurations and operator control.
The SCADA system covers larger geographical areas. It may rely on a variety of communication links such as Radio and Telephone
Closed loop control is not a high priority in this system.
SCADA is data-gathering oriented: The control center and operators are the center of its universe. The remote equipment is merely there to collect the data-though it may also do, some very complex process control.