There are radioactive sources americium 24 1 in the inner and outer ionization chambers. The positive and negative ions produced by ionization move to the positive and negative electrodes respectively under the action of electric field. Under normal circumstances, the current and voltage of the inner and outer ionization chambers are stable. Once smoke escapes from the outer ionization chamber, the normal movement of charged particles will be disturbed, and the current and voltage will change, which will destroy the balance between the inner and outer ionization chambers, so the wireless transmitter will send out a wireless alarm.
So choose AC.