This is the Multiplexer Driver card for the Low Level PIU.

This card monitors the selected point during a scan cycle to verify that the relay selected by the microprocessor has responded correctly, and that only one relay has responded. The mux driver card also has a relay voltage regulator, which receives +24 Vdc from the backplane and supplies +15 Vdc to drive the relays in the analog input cards.

This card has an LED to monitor relay power. The relay should be illuminated during normal operation.