Perpetual check themes - test positions

[Howard E]

The first one is an old one while the other two are from eng vs eng matches I ran.

[d]r7/8/4p2k/3p1bR1/7r/Np6/1P6/K5R1 w - - bm Rh5;
[d]8/6k1/6Pp/3r1P2/6K1/n3BP2/1p6/4R3 w - - bm Bxh6;
[d]1b6/1P4k1/6p1/6q1/2p2p2/2P2P2/1P3Q1K/5B2 b - - bm Ba7;

[Howard E]

#2 is not a perpetual check theme - sorry.
However it still is a useful test position for finding a draw in a difficult position.

#3 seems the most challenging, yet when the first two moves are entered most see the draw rather quickly.