Mike Nelson wrote on Mon, Sep 30, 2002 02:16 PM UTC:
Legally, triple repetition does not require any checks. However, by far the
most common triple-repetiton draws are those involving perpetual check. I
have never experienced any other type in any game I've played or
observed.
In older verisons of the FIDE laws, perpetual check was a drawing
condition in its own right--then someone observed that pepetual check
would alway eventually lead to triple repetition, allowing the laws to be
simplified.