Remote I/O and RTU

RTU (Remote Telemetry Unit), are controllers used at unmanned locations or remote locations, the strong point of this is Communication and logging facility which is not avaliable with PLC, RTU's always uploads the informations on demand of SCADA using dial up method, now a days there are RTU with web loading facilities. Ex:- Kingfisher RTU, typical applications are Remote water pump station, booster pump station, oil well head platforms. Remote I/O are the part of the main controllers, let me explain with example, asume that you have a main control station, connected to the process plant. You have Sub station located at some distantce, now instead of putting a separate PLC over there you can have only I/O rack kept over there and it is connected to the main controllers over ethernet or any other protocol. Like a combination of Allen Bradley Control logix with Flex I/O.