The following system requirements and limits apply to the Music on Hold feature, all audio streaming devices that are using the Music on Hold feature support simplex streams. The music on hold server supports at least 500 simplex streams. This music on hold server, which is installed as an option from Call Manager Administration, can coexist with other Cisco and third-party media applications. Just single music on hold server may be installed on a media convergence server, but the music on hold server may be installed on multiple media convergence servers. And for every single MOH audio server, you may define up to 50 audio sources. A Call Manager Administration window supports addition, update, and deletion of each audio source. The music on hold server also supports one fixed input source. The system supports the following codec: G.711 a-law/mu-law, G.729a, and wideband. Because the G.729a codec is designed for human speech, using it with music on hold for music may not provide acceptable audio quality, for each cluster, you may define up to 50 audio sources from files as well as one fixed audio source. A Call Manager Administration window supports addition, update, and deletion of each audio source. All servers use local copies of the same 50 or fewer files. You must set up the fixed audio source that is configured per cluster on each server, for each cluster, you may define at least 20, music on hold servers.

The Call Manager Administration window allows addition, update, and deletion of music on hold servers. The window allows administrators to specify the following characteristics for each server; Call Manager Administration allows definition of at least 500 media resource groups per cluster. Each media resource group may include any combination of at least 20 media resources, including music on hold servers, media termination points, trans-coders, and conference devices. Music on hold servers in one cluster supports at least 10,000 simultaneous, music on hold streams. The Call Manager Administration allows definition of media resource group lists. Alterations to the Call Manager Administration device configuration windows for phones and gateways allow the selection of a media resource group list, hold stream source, and consult stream source as optional parameters for a device. Modifications to the CallManager Administration Directory Number configuration windows allow selection of a user hold source and a network hold source. Modifications to the Call Manager Administration Service Parameters allows entry to a cluster-wide, default music on hold stream source (default specifies 1) and default media resource group type. And the number of streams that the music on hold server can use may decrease if the TAPI wav driver, software MTP, or software Conference Bridge is in use on the same MCS server.