How to set it up
In LinuxMCE Admin go to Wizard, Devices, Core and be sure the box "Text To Speech" is checked. That creates a Text To Speech device on the Core.
Now the security module will make announcements, like countdowns and warnings about tripped sensors, on your security announcement devices. Choose Wizard, Security, Settings by Alert type to add devices you want the security module to use. You can add media players, like Xine, and network audio players, like SqueezeBoxes.
Whenever you want to make your own announcement you will send the Text To Speech device a "Send Audio To Device" passing in as the Device parameter a list of the devices you want to hear the announcement on, and as the Text parameter what you want to hear. For example, you could go to Wizard, Scenarios, Lighting Scenarios. Add a scenario, edit it, choose "Advanced" from the using wizard pull-down, choose "Text To Speech" from the Device pull-down, choose "Send Audio To Device", from the Command pull-down, click 'Add'. In the parameter "#103 PK_Device_List (string)" type in a comma delimited list of the devices you want to make the announcement on, such as "38823,82827,28282". You can find the device numbers in LinuxMCE Admin by choosing Advanced, Devices, and selecting devices from the tree. It will say "Device Info #xxx" for each device. In the "#9 Text (string)" parameter type the announcement you want the Text To Speech device to send to the device.
Rather than using Text To Speech you can also record an audio/video file (wav, mp3, mpg, etc). Copy the audio file to your Core somewhere. You can do this using the network share. Note the public folder you access from the network share is in the directory "/home/public/data" on the Core. So, if you create a folder "Announcements" and put a file "GetOutBurglar.mp3" in there, the filename on the Core will be "/home/public/data/Announcements/GetOutBurglar.mp3". Now, instead of sending a command to Text To Speech, send a command to Media Plugin. You'll find that device is under Core->DCERouter->Media Plugin. Choose the command "MH Play Media", and for "#13 Filename (string)" put in the filename, and for "#45 PK_EntertainArea (string)" put in a comma delimited list of the Entertainment Areas in which you want to play the media. Don't worry about what devices to use--Media Plugin will figure that out. Put a 1 in "#116 Resume (bool)" which means that whatever media was previously playing in those areas will resume when this media finishes. The other parameters you can leave blank.