SIPLUS S7-300 SM 321 based on 6ES7321-1CH20-0AA0 with conformal coating, -25…+70 °C, digital input isolated 16 DI, 48-125 V DC, 1x 20-pole 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.