> How many digits are on the display of one of those phones? It seems > that you should be able to concoct something which is easy to compute, > and offers as much surety as the few digits on the display. You get 6 big characters that you can see from a couple of feet away, or three lines of 16 characters that you have to squint at ;-) (It's a 100 x 32 pixel graphic display). Eric