A [polymer network/liquid crystals (LCs)/chiral dopant] composite with a smectic A (S-A) <----> chiral nematic (N*) phase transition is prepared. A very drastic change from the light-scattering S-A phase to the transparent N* one is achieved upon heating the composite. The transparent state of the N* phase is 'frozen' in the S-A phase upon cooling. When an ac electric field is applied to the composite, the transparent S-A phase is changed into the light-scattering S-A one again.