Avaya

 supported IP phones

Send text notifications and response options

Send audio beep

Send image in .jpg format to models that support images

Convert text-to-speech, which uses multicast audio streaming

Per the 

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 developer documents, supported phones must be running H.323 software release 3.0 or later to support multicast audio streaming. 9601 SIP only does not support H.323 v 3.0, and therefore does not support text-to-speech.

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 IP phones do not support multiple DNs.

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 IP phones support only JPG image files.

The 

AtHoc

 Blast Activator sends a stop command to IP phones in accordance with the defined alert duration. However, this command is only capable of stopping an audio stream, which is only used with text-to-speech functionality. The 

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 API does not have a command to tell the phones to exit the browser or to set the screen to a different mode. The end user must manually clear the screen.

IP phones register to the System when they boot up. Registration does not go through 

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's Call Manager