Siemens 6ES7321-1BH02-0AA0 Digital Input Module

Siemens 6ES7321-1BH02-0AA0 is a SIMATIC S7-300 SM 321 digital input module that provides 16 DC 24 V input channels on a single 20-pin front connector. The 1BH02 suffix identifies it as optically isolated between field wiring and the backplane, making it suitable for noisy industrial environments and safer CPU operation. As an expansion module for the S7-300 family, it plugs into the SM 321 input module backplane and wires 24 V sensors or switches to its 16 input points, enabling straightforward integration of devices such as pushbuttons, limit switches, and other digital sensors into ladder logic or function block programs. The 16 inputs are designed for DC 24 V signals, supporting reliable digital sensing across automation, machine control, and process lines where additional input capacity is required for a S7-300 PLC system. The part number 6ES7321-1BH02-0AA0 corresponds to the SM 321, DI 16xDC 24 V optically isolated with a 20-pin front interface; Siemens also offers related galvanically isolated variants (for example, 6ES7 321-1BH10-0AA0) to suit different isolation preferences and wiring needs.