Can I use the extra relays on AEC reader boards as auxiliary relays?
Yes. Reader Board 1 has three spare relays (5, 6, 7) and each subsequent Reader Board has four spare relays (5, 6, 7, 8). Each board locally has relays 1-8, and as the Reader Boards are addressed, the relay numbers take on the Reader Board address scheme. Therefore, you could say locally each Reader Board has relays 1-8, but Reader Board 3 addresses its relays as 17-24.
Relays numbered 1-4 are predefined on each Reader Board for the output to Doors 1-4. Relay 8 on Reader Board 1 is predefined as the Common Alarm Output. This is designed for integration with an intrusion panel, such as the D9412GV2 via a supervised input.