https://en.wikipedia.org/wiki/Access_control
"Physical security access control with a fingerprint scanner" by Lgate74 - Own work. Licensed under CC BY 3.0 via Commons - https://commons.wikimedia.org/wiki/File:Physical_security_access_control_with_a_fingerprint_scanner.jpg#/media/File:Physical_security_access_control_with_a_fingerprint_scanner.jpg
"Access control door wiring" by Andriusval - Own work. Licensed under Public Domain via Commons - https://commons.wikimedia.org/wiki/File:Access_control_door_wiring.png#/media/File:Access_control_door_wiring.png