The man who saves Stephen Hawking's voice - opinion - 30 December 2011 - New Scientist

"the most interesting thing in my office is a little grey box, which contains the only copy we have of Stephen's hardware voice synthesiser. The card inside dates back to the 1980s and this particular one contains Stephen's voice. There's a processor on it which has a unique program that turns text into speech that sounds like Stephen's, and we have only two of these cards. The company that made them went bankrupt and nobody knows how it works any more."