  The duality approach in 2-{\it dim} two-component regular checkerboards was
extended onto piezoelectricity and piezomagnetism problems. There are found a
relation for effective piezoelectric and piezomagnetic modules for the
checkerboard with $p6^{\prime} mm^{\prime}$-plane symmetry group ({\em
dichromatic triangle}).
  \pacs{Pacs: 73.50.Bk,Jt, 75.70.Ak, 77.65.-j, 77.84.Lf}
