The Voicemail Pro application can use Text-to-speech (TTS). It does this using either locally installed TTS files or, for subscription IP Office systems, TTS provide by Google services.
Google TTS does not require any installation, just configuration of the Speech UI setting in the IP Office system configuration. When configured, Google TTS overrides locally installed TTS.
The process below covers the installation of local TTS files. The TTS languages are downloadable as 3 separate ISO images. You need to upload and install the additional languages on the server or servers running Voicemail Pro.