This question is not particularly Reds related, but is baseball related. I have been impressed with the accumulated baseball knowledge here and can't find an answer anywhere else. So here goes.
One of our local teams was playing in the state playoffs the other day and the opposing coach was calling pitches by flashing three numbers to the catcher. The catcher would then look at his wristband, which tells him the pitch and location. Then the catcher signals the pitch to the pitcher, then moves to the desired location. My coaching partner for the past several years in youth baseball was interested and asked the coach after the game about this system. The coach said he has 125 options (five fingers cubed, I guess) so he can call the same pitch many times in a game without using the same three numbers. For example, a fastball inside and high might be 2-3-2 one time and the next time he calls a fastball inside and high it might be 4-2-5. The coach said he knows several high schools and many colleges are using the system, but didn't think any MLB teams were.
Does anyone have more knowledge about this that they can share? I have googled pitch calling, location, pitching zones, etc. and can't find any site on the Web with this information.