Local I/O is directly connected to the processor elements of the control system. Remote I/O has some additonal communication hardware which allows it to be located at a site distant from the controller, connection being via some form of data cable. It potentially saves a lot of field wiring by allowing the I/O to be located near the point of use, but without the cost or complexity of installing another controller.
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The local input/output modules require signal wiring to the processor location. You could install remote modules near the process to reduce cables to the processor area; or install remote capable modules at the processor.
Hi,
Local I/Os means the I/O modules which are connected direvtly to the controller. Local I/Os communicate directly with the controller
Remote I/Os are placed in bases remotely from the controller, and controller controls these I/Os via a special module call Remote Master. Each remote base has one Remote slave module which communicates with the Remote master using various protocols (like serial, ethernet, or some properitory protocol of the manufacturer).
For more information you can check this link
