AC Safety Capacitors Johanson Dielectrics AC Safety Capacitors are ceramic chip capacitors designed for AC voltage surge and lightning protection in line-to-ground interface applications in computer networks, modem, facsimile, and other equipment. The AC Safety Capacitors from Johanson are available in four different case sizes and either NPO or X7R dielectric material. These capacitors are surface mountable and offer 250VAC voltage and capacitance range from 5pF to 4700pF.