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From our admin guide
7.2.24. Streaming Audio Server – SAS
This feature allows one to attach an audio source to one of the SPA FXS ports and use it as a streaming audio source device. The corresponding Line (1 or 2) can be configured as a streaming audio server (SAS) such that when the Line is called, the SPA answers the call automatically and starts streaming audio to the calling party provided the FXS port is off-hook. If the FXS port is on-hook when the incoming call arrives, the SPA replies with a SIP 503 response code to indicate "Service Not Available." If an incoming call is auto-answered, but later the FXS port becomes on-hook, the SPA does not terminate the call but continues to stream silence packets to the caller. If an incoming call arrives when the SAS line has reached full capacity, the SPA replies with a SIP 486 response code to indicate "Busy Here". The SAS line can be setup to refresh each streaming audio session periodically (via SIP re-INVITE) to detect if the connection to the caller is down. If the caller does not respond to the refresh message, the SAS line will terminate the call so that the streaming resource can be used for other callers.
7.2.25. Music On Hold – MOH
On a connected call, the SPA may place the remote party on call (the only way to do this on te SPA- 2000 is to perform a hook-flash to initiate a 3-way call or to swap 2 calls during call-waiting). If the remote party indicates that they can still receive audio while the call is holding, the SPA-2000 can be setup to contact an auto-answering SAS as described in Section 4 and have it stream audio to the holding party. When used this way, the SAS is referred to as a MOH Server.
