A biometric reader can be used as a standalone security device or in combination with a card reader or a keypad. In the second scenario, a user also has to authenticate themselves by means of presenting a proximity card or pressing an access code. This way a two-factor authentication is achieved.
Biometric readers are mostly used in areas where an extra layer of security is required such as data centers and financial institutions. Although biometric readers are considered to be the most reliable, they are also more expensive compared to other access control authentication devices.