What are the jumpers on the ADC-AC-X100 for?

J1

The J1 jumper is the end-of-line termination jumper. It should only be set to IN if the expansion is the last in the chain of expansions connected to a controller.

For more information about wiring and end-of-line jumper configurations, see Wire and configure an X100 Two Reader Expansion Module (ADC-AC-X100) to an X1100 Door Controller (ADC-AC-X1100).