Siemens 6ES7 321-1BH02-0AA0 Digital Input Module (SM321) provides 16 channels of digital inputs at 24 V DC for SIMATIC S7 controllers. It is listed as SM321 DI 16xDC24V with article number 6ES7 321-1BH02-0AA0, designed for use in SIMATIC S7-300 backplane configurations with grouping of 16 inputs. Each channel accepts a 24 V DC field signal to feed the PLC’s input logic. Typical uses include reading binary field devices such as sensors and switches in industrial automation setups.
