All access control units make autonomous decisions by default, relying on the access control settings downloaded from Security Center during unit synchronization. The unit only falls back on the Access Manager when it is presented with an unknown credential.
The access control unit is operating online when it is connected to its Access Manager. The unit makes decisions on its own, based on the access control settings (access rules, cardholders, credentials, unlock schedules, and so on) downloaded from Security Center when it was last synchronized.
When the access control settings are changed in the system, the Access Manager automatically updates the units that are affected by the change, every 15 seconds. For HID units, you also have the option to configure the synchronization to be carried out daily, weekly, or on demand. When an unknown credential is presented, the unit immediately queries its Access Manager in order to carry out the correct decision, and thus, updates its memory at the same time.
As long as the unit remains connected to its Access Manager, it reports every decision it makes (Access granted and Access denied) and all activities (Door opened, Door closed, Entry detected, and son on) in real time to the Access Manager. The Access Manager can override a decision to deny access if it contradicts the current settings in Security Center.
The access control unit is said to operate offline when the connection to its Access Manager is lost. When operating offline, the unit appears in red in Config Tool and Security Desk.
Although offline, the unit continues to make access control decisions based on the information previously downloaded through the Access Manager during synchronization. The difference is that the Access Manager is no longer able to override any deny decisions, nor to update the unit when settings are changed in Security Center. All activities are logged locally on the unit, and are uploaded to Security Desk when the connection with the Access Manager is re-established.