Various Access : YDM4109 has multiple options to access the lock- Fingerprint, Pin Code, Key Override, Bluetooth (via Yale Link app). With Yale App and Wifi-bridge you can lock or unlock your door, share keys with family and friends, get notifications when someone comes home and more, all from one mobile app. Internal Forced Lock : It is a security-enchancing function that 'disables' authentication methods such as passwords, RFID cards and fingerprints from outside when setting up functions indoors. Low battery alarm and emergency power supply terminal : It warns in case of low battery with alarm and LED. When the batteries are completely discharged, you can easily supply emergency power to the lock with a standard 9V battery. Service Assurance: 24X7 Toll free Customer Support helpline for Installation & Service Support.