In article ,
"Paul Ekins" writes:
I would like to know what happens when theres a power cut....


One would expect some sort of battery back up would be required.

In an office environment, typically battery backup for 250 operations
(and a time limit, like 24 hours). Of course, you might also have lost
access to the security vetting system which could mean staff entitled
to access might be locked out because security system can't verify them.
In that case, and after the battery has died, it's physical key operation
just like a conventional door lock.

--
Andrew Gabriel