Rule: Bid a takeout double when you are short in the opponent’s suit and long (at least 3 cards) in all the unbid suits.
But:
Opp. You
1♣ ??
#5 #6 #7
♠ J 10 7 2 ♠ A Q 9 7 6 ♠ A J 9
♥ A Q 9 8 ♥ J 9 8 ♥ K Q 7
♦ K 9 ♦ Q 7 6 ♦ 10 9 6 4 2
♣ A 10 9 ♣ A 2 ♣ A Q