Never seen this before

[Ump Rube]

An appeal can only be asked on a swing that the PU has considered check and the pitch was ruled a ball. You cannot appeal a swing that has been considered a strike. So here is the thought pattern:

1. Was the pitch a strike? If yes: STRIKE, if no: continue to #2.
2. Did the batter strike at the pitch? If yes: STRIKE, if no: continue to #3.
3. Rule pitch a BALL. If coach appeals swing only, continue to #4.
4. Ask BU if player struck at ball. If yes: STRIKE, if no: ball stands.