An Access Control Unit (ACU) is a panel to which all door-locking hardware (see Electric Strike and Mag Lock) and credential readers are connected. The ACU functions as the traffic controller as well as the primary power source for all the devices connected to the access control system.
When a valid credential is presented to a reader located at a door, the ACU temporarily interrupts the power supply to that door’s locking method (which is set up in a fail-safe mode), allowing the user to enter.