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I/O Device
Refers to any control or monitoring hardware that conveys information to or from PLC's.
Instruction set
Instructions that are available to program the PLC.
Interfacing
Connection of a PLC to external devices.
Incremental
This term typically refers to encoders. Encoders provide logic states of 0 and 1 for each successive cycle of resolution.
Integrated Circuit
A collection of electronic devices working together.
Intelligent I/O
PLC modules that have a microprocessor built in. An example would be a module that would control closed-loop positioning.
I/O (input / output)
Used to speak about the number of inputs and outputs that are needed for a system, or the number of inputs and outputs that a particular PLC can handle.
I/O port
A channel through which data is transferred between an input or output device and the microprocessor. The port appears to the PLC as one or more memory addresses that it can use to send or receive data.
IPX/SPX (InterPacket eXchange/Sequential Packet eXchange)
Networking protocol used for some LAN operating systems.
IP rating
Rating system established by the IEC that defines the protection offered by electrical enclosures. It is similar to the NEMA rating system.
Isolation
Used to segregate real-world inputs and outputs from the CPU. Isolation assures that even if there is a major problem with real-world inputs or outputs (such as a short), the CPU will be protected. This isolation is normally provided by optical isolation.
ISDN (Integrated Services Digital Network)
A digital based communication technology supporting both voice and data.
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