With the Multi Device Access (MDA) feature, a user can access calls on multiple devices of various capabilities, but using the same number. All devices of the user will ring for an incoming call, and the user can answer with the chosen device or a paired mobile device. After the call is answered, the remaining devices stop ringing. If the user wants to use a device with better capability, the user can join the existing call using that device. Hence, a conference is created on ACM and the user can manually disconnect the previous device. This procedure is known as a handoff. In case of an AAC-hosted conference, the last MDA device to join the call remains active and all earlier devices are dropped.

The Multi Device Access feature consists of the same user and extension using the same AOR to register multiple devices to Session Manager. All registered devices ring simultaneously and the device on which the user takes the call becomes a device with the active call. Other paired MDA devices receive notification of the active call and dialog information. The paired MDA devices can join the call using this dialog information. The display shows a two-party call, and not a conference. Only one active MDA call is maintained for a call involving AAC.