Impacted by shrinking municipal budgets, many water/ wastewater plants and facilities operate frugally, often running on systems plagued with obsolete hardware and software and patched with years of Band-Aid fixes to remain functional. These patches are not always recorded properly when they are made, and over time, the initially accurate documentation about a facility's control system can become scarce or unreliable, making it difficult to troubleshoot or upgrade the system when necessary. Looking at the history of programmable logic controllers (PLCs) often used in these facilities, the intent for these devices was to create an industrialized controller to replace electromechanical relay logic (see Figure 1). The world of the electrician/technician was transitioning into the world of the computer programmer. Even as this occurred, electricians maintained a strong influence on PLCs, which were destined to stay in their domain.
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