RAG128 is an intelligent, eight channel, 12-bit, analog-to-digital converter unit that interfaces to a host computer through an opto-isolated asynchronous serial port. It is packaged in a steel enclosure for remote installation and input connections are via screw terminals on the card. Communication with the host computer is via EIA RS-485 serial communications. ASCII-based command/response protocol permits communication with virtually any computer system that has an RS-485 port. ASCII-based programming permits you to write applications in any high-level language that supports ASCII string functions. As many as 31 RAG128's may be connected on a single two or four wire multidrop network. Each unit has a unique address and communication uses a master/slave protocol wherein the unit talks only if questioned by the computer. The unit's address is programmable from 00 to FF hex and whatever address is assigned is stored in EEPROM and used as the default address at the next power-on. Similarly, baud rate is programmable for 1200, 2400, 4800, 9600, 14400, 19200, and 28800. The programmed baud rate is stored in EEPROM and used as default at the next power-on. A type 8031 microcontroller (with 32K x 8 bits RAM and 32K x 8 bits EEPROM and a watchdog timer circuit) gives RAG128 the capability and versatility expected from a modern distributed control system. RAG128 contains lowpower CMOS circuitry, an opto-isolated receiver/transmitter, and power conditioners for local and external isolated power. It can communicate at baud rates up to 28.8K baud and distances up to 4000 feet with low-attenuation twisted pair cabling.