What type of access control system requires a multi-digit number for entry?

A keypad access system requires a multi-digit number for entry, which typically involves the use of a Personal Identification Number (PIN). This system works by allowing authorized users to enter a specific sequence of numbers on a keypad to gain access to secured areas or resources. The reliance on a numeric code enhances security by ensuring that only individuals with knowledge of the correct PIN can enter.

In contrast, biometric systems utilize unique physical characteristics, such as fingerprints or facial recognition, while card access systems rely on RFID or magnetic swipe cards to authenticate users. Physical key systems require a physical key to unlock a door or mechanism, which does not involve any electronic input or numeric code at all. Thus, the keypad access system stands out as the option specifically designed for entering a multi-digit number for access control purposes.