The Siemens 6ES7221-1BH22-0XA0 Digital Input EM 221 module is a spare part for SIMATIC S7-200 systems, designed for use only with S7-22X CPUs. It provides 16 DC digital inputs at 24 V DC, with support for sinking or sourcing input wiring. Each input channel draws a typical high-state current of 4 mA, and recognizes a low with 0–5 V and a high with +15 to +30 V. Common applications include monitoring 24 V sensors and switches—such as pushbuttons, limit switches, and proximity sensors—in industrial automation panels.
