The connection through the AIU is passive. Connecting the load to an AIU can simplify cabling configurations. Typical Digital Output circuit is depicted. Digital Outputs are optically isolated solid state switches. Typical DO circuit is depicted.
DOs are optically isolated solid state switches.
Protective diode CR1 is necessary. Select a relay with an internal protective diode or use a discrete diode, 1N4001 or equivalent. Failure to use a protective diode may result in damage to the RIU . Typical DO circuit is depicted.