The Contact Closure feature is a controllable relay providing dry contacts for various applications. To implement Contact Closure, you must connect an Avaya Partner Contact Closure adjunct box to the CCA port on the Branch Gateway chassis. The adjunct box provides two contact closures that can be operated in either a “normally closed” or “normally open” state. Contact closures can control peripheral devices, for example, devices that automatically lock or unlock doors, or voice recording units. You can configure the CCA port so that the connected devices are controlled by an endpoint device, such as a phone. For example, a user can unlock a door by entering a sequence of digits on a phone keypad.