SIPLUS S7-300 SM 321 20-pole based on 6ES7321-7BH01-0AB0 with conformal coating, -25…+70 °C, digital input isolated 16 DI; 24 V DC, 1x 20-pole, hardware interrupt, diagnostics, suitable for isochronous-mode operation 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.