The Contact Closure feature is a controllable relay providing dry contacts for various applications. To implement the contact closure feature, 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 you can operate in a normally closed or normally open state. The contact closures can control auxiliary devices, such as devices that automatically lock or unlock doors or voice recording units. You can configure the CCA port so that an end device, such as a phone, can control the connected devices. For example, a user can unlock a door by keying a sequence into a phone keypad.