What constitutes an industrial control system (ICS) or supervisory control and data acquisition (SCADA) system and the environments in which they operate has changed drastically over the last decade or so. Traditionally, ICS were used in discrete and batch manufacturing, process control, packaging, and infrastructure. Some may argue the fine points of that list, however, the key point is that it is limited to a small group of systems and industries.

As computing platforms and networks have become cheaper, smaller, and easier to use, the number of places where control systems are being applied has expanded. Industries like medical, transportation, logistics, heating, ventilation, and air-conditioning (HVAC), aviation, and others have all adopted control system hardware and techniques. All of these industries have found that by automating different aspects of their systems, they can improve their reliability and efficiency.

It is now more important than ever for end-users, integrators, and vendors to understand how different devices and systems will perform under different conditions. Devices and systems designed for a particular industry or environment may have similar functionality to those designed for another industry, but may have very different performance characteristics.

It is probably a good idea to take a step back and think about what makes something an ICS. In its basic form an ICS collects information about its environment, interprets that information in some way, makes decisions based upon that information, and takes some actions based upon those decisions. Generally, some or all of those steps are automated in some way. Modern ICS heavily use computer-controlled automation to accomplish these steps.

As with personal computers, computer-controlled automation systems have increased in performance over the years and have found their way into an ever increasing number of locations. Devices that already had some measure of computer intelligence have increased in power and other devices have added computer intelligence to increase their functionality.

Using the basic definition of an ICS above, it is possible to see that many more systems can be consisted ICS than were traditionally. Take, for example, a railway switch yard. The system senses trains and cars passing through the yard. The track switches are set to allow a particular engine to couple with a certain set of cars and then proceed to the correct track. The switches themselves are probably not manually operated any longer, but commanded by an operator. Some trains and cars have sensors that tell the switch yard systems more information. With that additional information, a control system could automatically direct the track switching system while a human operator monitors the system instead of actively controlling it.

Another example might be a hospital. The HVAC system for the facility is almost invariably run by a control system. Some of the HVAC plumbing may be isolated, however the controllers are probably still connected to the centralized control system. In addition, the patient monitoring system is effectively like a small SCADA system. Patients and their medical equipment is outfitted with a series of sensors that provide information to a centralized monitoring system. The operators (doctors and nurses) monitor the condition of the patients and their related equipment. If something is amiss, then one of the operators takes an action to remedy the situation. In a hospital, these may be manual or automatic actions by the operators.