Control systems may be pneumatic, analog, digital, or a combination of the three. Older designs utilized pneumatic control for local control loops. Analog control systems were an industry standard for a short time before quickly being replaced by digital control systems. The present industry standard is for a distributed control system (DCS), a programmable logic controller (PLC), or a direct digital controller (DDC) to provide digital control logic based on information gathered from electronic sensor inputs and responding with electronic control of pneumatic or electric powered valves and dampers.
ThriftBooks sells millions of used books at the lowest everyday prices. We personally assess every book's quality and offer rare, out-of-print treasures. We deliver the joy of reading in recyclable packaging with free standard shipping on US orders over $20. ThriftBooks.com. Read more. Spend less.