Siemens 6ES7221-3BD30-0XB0 is an SB 1221 digital input module for SIMATIC S7-1200 controllers, providing four 24 V DC digital inputs. It operates as a sourcing input board (L+ with a 5.0 V DC reference) and supports up to 200 kHz input signaling. As an expansion card for S7-1200 CPUs, it extends I/O with four independent digital inputs that can be wired to external 24 V sensors or switches, using the SB 1221 family for seamless integration.
