At this point, I haven't yet been able to figure out just what means the original engineers used in order to accomplish this, but I'm very curious. Any insights that you can offer would be greatly appreciated.
I'll have a look for a way of playing back an audio file. Telephone exchanges use 8k 8bit samples per second which I think the UNO should be able to do.
Thanks. Supermarionation provided an interesting read. As it turns out, Jerry Anderson used this technique in the Thunderbirds series in the 60s.