When Enable external music on hold port is checked, music on hold for internal calls is automatically enabled and cannot be disabled. If an audio file is selected and the external music-on-hold port is also enabled, the music input from the external port takes precedence. The selected audio file serves as a backup music source if the external source fails or is not available.
Did you ever find a solution to the UC560 not playing external MoH? I have a box with 8.0.2 loaded and external MoH is not working. When you check the box for external MoH in CCA, it does not keep the checkmark in the box after exiting. When you go back into it, the checkmark is gone.
Configure Multicast Paging on the Cisco IP Phone 7800 Series or 8800 Series Multiplatform Phone
The Cisco IP Phone 7800 and 8800 Series Multiplatform Phones provide voice communication over an Internet Protocol (IP) network...
Add Call Park on a Cisco 7800 or 8800 Series Multiplatform Phone Key Expansion Module
Call park allows the user of the phone to put an incoming call on hold so that the call can be retrieved on another phone. A call is park...