SIPLUS S7-300 SM 321 20-pole based on 6ES7321-1FF01-0AA0 with conformal coating, -40…+70 °C, digital input isolated 8 DI, 120 V/230 V AC Just like the CPU, the digital input modules are also protected against extreme ambient conditions. Due to the 100% conformal coating they can withstand biologically, chemically and physically active substances, condensation, frost, and corrosive gases. Regardless of the conditions, your digital signals are reliably recorded.