Control systems are built with hydraulics, pneumatics and electrical components. PLCs are used to signal mechanical devices and to monitor feedback. An HMI gives an operator a viewpoint of the components and creates an interface. Troubleshooting control systems involves having system knowledge in all these applications and components or specializing in hardware, electronics, mechanical or software. Otherwise, a good systems approach will allow an engineer or a non-degreed technician or technologist to troubleshoot any of these components.