A take-out double has no upper limit of strength and may be the first move on a really big hand.
The effort to separate penalty doubles from take-out doubles has become more difficult in recent years, as experts have developed special agreements about some low-level situations.
North-South were playing negative (take-out) doubles of overcalls, so South either had to pass - hoping that his partner would re-open with a take-out double that could be passed - or begin with a negative double.
It's a take-out double by the defense after your partner has bid.
You can make a take-out double with two cards in the opponent's suit but just remember, the worse your distribution the more points you should have.