Here you can choose the text-to-speech engine used for computer generated voices.
TTS Engine
You might find that the pronunciation of the name and notes are hard to understand over the phone. That is because the free text-to-speech engine provided by Microsoft tends to produce poor sound. For better and natural voices, you need to have a better text-to-speech engine.
Voicent do have a better text-to-speech engine. More details and tryout can be found online at http://voicent.com/text-to-speech-telephony.php. You can choose either a male voice or a female voice.
You can hear the computer generated voice by selecting Operation > Save TTS audio to file.
Pre-recorded Voice Selection
For date, number, time, and phone number, the gateway has both male and female voices.