Siemens 6ES7 321-1BH50-0AA0 SM321 is a 16-channel digital input module for the SIMATIC S7-300 family that provides isolated 24 V DC inputs. It is a source-input, 16‑point module with optical isolation and a 1×20 backplane interface for connection to the PLC. The inputs are active-low, making it ideal for reading 24 V DC field devices such as sensors and switches in automation panels.
