Surge arrester in a combined design for the power and data side. Pressure-resistant encapsulation for use in potentially explosive areas in Zones 1 and 2, to protect a 120/230 V mains supply and a 24 V data interface of field devices. Additional safety thanks to the confusion-proof Y-circuit for the 120/230 V mains supply. Universally applicable in Ex Zones 1 and 2 thanks to design II 2 G Ex d IIC T5/T6.