Siemens 6ES7321-1EH01-0AA0 is a SIMATIC S7-300 digital input module (SM 321) offering 16 optically isolated inputs for 120 V AC logic signals. It is designed to install in a SIMATIC S7-300 I/O rack and connect to the backplane to monitor field devices, providing channel-by-channel isolation for noise immunity. Typical uses include reading signals from industrial sensors, pushbuttons, and limit switches in automation systems that operate on 120 V AC input levels.
