David Griffith wrote: > It certainly is of interest. I'd like to get one of those for > myself. It shouldn't be too terribly hard to homebrew one of these > things into a shoeshine box, right? "Pennywhistle", Popular Electronics, March 1976. If you don't really need a design that old, you might be able to find a TMS99532 or Am7910 FSK modem chip. Eric