Keypads are button based mechanisms in both System Shock and System Shock 2 that regulated entry through the doors that they controlled. They needed the code to open them or they could be hacked.
They are encountered by the Hacker on Citadel Station.
System Shock 2
They are encountered by SOLDIER G65434-2 on the Von Braun and UNN Rickenbacker and were
manufactured by TetraCorp.