Access Control

Access control system components include:
An access control panel (also known as a controller)
An access-controlled entry, such as a door, turnstile, parking gate, elevator, or other physical barrier
A reader (such as card reader, biometric reader) installed near the entry. (In cases where the exit is also controlled, a second reader is used on the opposite side of the entry.)
Locking hardware, such as electric door strikes and electromagnetic locks
A magnetic door switch for monitoring door position

(Wikipedia)