Following are the main components of the RTU

1. Station Controller
2. Different cards – DI, DO & AI

A set of 5 cards, plus separate power supply & communication module are mounted in a single enclosure. Two such enclosures are mounted in the RTU using rubber pads & gaskets. This protects the cards from vibrations.
Control outputs (DO) are interfaced to a contactor which in turn is interfaced with CB trip or close coils. The power supply of the RTU is designed for 110VDC input, but can also switch-over to 230VAC. A wide variety of MODEMs suited for different media (e.g. leased line, Fiber-optic, Dial-up, GSM, PLCC, etc.) can be incorporated in the RTU

ARTU1 - ASHIDA RTU for small sub-stations

ARTU1 is a customized implementation of various ASHIDA SCADA components & modules. ARTU1 is ideally suited for small sub-stations with up-to 64 numerical relays on IEC103 protocol. The status/ control and Analog inputs which cannot be monitored from relays, can be hardwired to the FCCM/3(DI), FCCM/5B (DO) or FCCM/4B (AI) cards mounted inside the RTU.
The simplified over-all scheme can be shown in the following diagram

The system consists of SCADA Software on servers at Remote Control Center (RCC Equipment), Communication Media and RTUs at the remote stations. The RTU in turn acquires most of the status/ alarm information from communicable protection relays.
Main parts of ASHIDA RTUs (ARTU1) are a Station Controller, DI/DO & AI Cards and other accessories. The design is different from conventional RTUs in that it interfaces with AI, DI & DO cards using communication link rather using hard-wired communication. Although this necessitates that all cards have a separate controller of its own, it has been so designed so that RTU can interface with communicable protection relays & communicable Multi-function electrical meters. Thus making the RTU virtually future-proof.