does the coach have to have a player at the table to replace DQ player at the 20 second horn? i think this was a POE last year. i dont have a case book with me, is this considered a direct T to the coach?
thanks for the help.

No. The 20 second horn is a warning that the coach has 10 seconds left to get a sub in. It's a T when the 30 second horn sounds.

If I'm administering the substitution for the disqualified player and they don't have a replacement by the 20sec horn. I just keep saying "White we need a replacement, white we need a replacement..." until they bring one in. It's worked so far, I haven't had to T anyone up for this yet.