Abstract: The text to speech (TTS) system comprises two main components, a linguistic processor and an acoustic processor. The former is responsible for receiving an input text, and breaking it down into a sequence of phonemes. Each phoneme is assigned a duration and pitch. The acoustic processor is then responsible for reproducing the phonemes, and concatenating them into the desired acoustic output. The TTS system is driven from the output in that the linguistic processor does not operate until it receives a request from the acoustic processor for input. This request, and a return message that it can now be satisfied, are routed via a process dispatcher. By driving the system from the output, the system can be accurately halted in the event that the acoustic output needs to be interrupted.