[M&M Guy]

This is what I've always thought was a long switch:

In 2-person, L calls a foul in the front court on the offense, reports the foul and now goes down the court to be new L, while the old T comes in to administer the throw-in. In 3-person, the same "long switch" happens if C is opposite the table, L calls the foul, old T comes down to administer the throw-in, and old L goes down the court and becomes new L. In both cases, the calling official is essentially going the entire length of the court, from one endline to another, or a long switch.

When officials talk about "no long switches", that means if L calls the same foul, they step out to report the foul, then go back to the same spot to administer the throw-in. The positioning is handled the same way as a violation in the backcourt, and no official ends up going the entire length of the court.