Hi Dan yes you are quite correct it was indeed the Tefifon, I couldn't remember its name. It certainly is a very strange device. The one they had at the museum of communication wasn't in working condition at the time, they were in the process of trying to repair it I hope they succeeded. I must thank you for bringing this up as I really enjoyed rewatching the YouTube video link you gave which gives an excellent introduction of the device. The sound quality seemed surprisingly good. I watched the video while sitting out in the sun in my back garden. All the best MrX