What effect does losing communication with the server have on an access controller?
The ISC has its own memory, and it will run locally from its own database. The ISC itself will not be effected by a communication loss unless it runs out of transaction memory, or it operates any global functions. Any readers providing access without global anti-passback will not be effected.
When the ISC has an upstream communication failure with the communication server and/or linkage server, global features will cease to function. This includes features such as Scheduler, Guard Tour, Global Anti-Passback, and Global Input/Outputs.
If there is a failure upstream to the communication server from an ISC, the linkage server, global output server, and any other server service that requires activity from the offline access panel will not run any functions associated with the events from that panel (i.e. an e-mail will not be sent on an Access Granted from the ISC if the ISC is offline with the communication server).