page_title: Computer appliance
section_title: Appliances in industrial automation
hierarchical_section_title: Computer appliance / Appliances in industrial automation
caption_attribution_description: Siemens Simatic S5 PG 635 programmiergerät für PLC.
context_page_description: A computer appliance is a computer with software or firmware that is specifically designed to provide a specific computing resource. Such devices became known as appliances because of the similarity in role or management to a home appliance, which are generally closed and sealed, and are not serviceable by the user or owner. The hardware and software are delivered as an integrated product and may even be pre-configured before delivery to a customer, to provide a turn-key solution for a particular application. Unlike general purpose computers, appliances are generally not designed to allow the customers to change the software and the underlying operating system, or to flexibly reconfigure the hardware.
  Another form of appliance is the virtual appliance, which has similar functionality to a dedicated hardware appliance, but is distributed as a software virtual machine image for a hypervisor-equipped device.
context_section_description: The world of industrial automation has been rich in appliances.  These appliances have been hardened to withstand temperature and vibration extremes.  These appliances are also highly configurable, enabling customization to meet a wide variety of applications.  The key benefits of an appliance in automation are:
  Reduced downtime - a failed appliance is typically replaced with a COTS "commercial off-the-shelf" replacement and its task is quickly and easily reloaded from a backup.
  Highly scalable - appliances are typically targeted solutions for an area of a plant or process.  As the requirements change, scalability is achieved through the installation of another appliance.  Automation concepts are easily replicated throughout the enterprise by standardizing on appliances to perform the needed tasks, as opposed to the development of custom automation schemes for each task.
  Low TCO (total cost of ownership) - appliances are developed, tested and supported by automation product vendors and undergo a much broader level of quality testing than custom designed automation solutions.  The use of appliances in automation reduce the level of testing needed in each individual application.
  Reduced design time - appliances perform specific functions and although they are highly configurable, they are typically self documenting.  This enables appliance based solutions to be transferred from engineer to engineer with minimal need for training and documentation.
  Types of automation appliances:
  PLC (programmable logic controller) - Programmable logic controllers are appliances that are typically used for discrete control and offer a wide range of Input and Output options.  They are configured through standardized programming languages such as IEC-1131.
  SLC (single loop controller) - Single loop controllers are appliances that monitor an input variable and effect change on a control output (manipulated variable) to hold the input variable to a setpoint.
  PAC (programmable automation controller) - Programmable automation controllers are appliances that embody properties of both PLCs and SLCs enabling the integration of both analog and discrete control.
  Universal gateway - A universal gateway appliance has the ability to communicate with a variety of devices through their respective communication protocols, and will affect data transactions between them.  This in increasingly important as manufacturing strives to improve agility, quality, production rates, production costs and reduce downtime through enhanced M2M (machine to machine) communications.
  EATMs (Enterprise Appliance Transaction Modules) - Enterprise appliance transaction modules are appliances that affect data transactions from plant floor automation systems to enterprise business systems.  They communicate to plant floor equipment through various vendor automation protocols, and communicate to business systems through database communication protocols such as JMS (Java Message Service) and SQL (Structured Query Language).
caption: Back of a Siemens programmable logic controller (2013)
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