The 104-IIRO-8 is a low-cost card that provides isolated input and output for PC/104 Bus computer applications. The card has eight optically-isolated digital inputs for AC or DC control signals, eight TTL Inputs and eight electro-mechanical relay outputs. An Economy version can be ordered as Model 104-IIRO-8E which has no Change of State Dectection or IRQs. INPUTS The isolated inputs can be driven by either AC or DC and are not polarity sensitive. Input signals are rectified by photo coupler diodes. A 1.8KΩ, ½ Watt resistor in series provides current limiting. The input voltage range is 3V to 28V (rms). To extend the input voltage range, you may connect external resistors in series with the input. Each input circuit is switch selectable for slow/fast filter that has a 4.7 millisecond time constant. The filter must be selected for AC inputs in order to eliminate response to AC noise. The filter is also valuable for use with slow DC input signals in a noisy environment. The filter may be switched out for DC inputs in order to obtain faster response. Filters are manually switched individually on or off. INTERRUPTS Interrupts are enabled/disabled by software. When the change-of-state detection circuit is enabled, the card asserts an interrupt whenever any of the eight isolated inputs change state. Once an interrupt has been generated and serviced, it is automatically cleared. This feature greatly frees up system resources by eliminating the need for constant polling to see when an input has changed state. OUTPUTS The electro-mechanical relay outputs are comprised of one group of eight form C SPDT outputs. The relays are all de-energized at power-on. Data to the relays is latched. CONNECTIONS The I/O is accessed via a 50 pin header type.