Siemens 6ES7 321-1BH02-0AA0 Digital Input Module

Siemens 6ES7-321-1BH02-0AA0 is a SIMATIC S7-300 SM321 digital input module that provides 16 isolated 24 V DC inputs (DI 16xDC24V) for converting field signals into PLC logic levels. Each channel accepts a standard 24 V logic signal from sensors, switches, or other discrete devices, feeding the S7-300 CPU through a 20‑pole backplane interface while maintaining galvanic isolation between field wiring and the controller electronics. As an expansion card in a SIMATIC system, it enables scalable digital input coverage for automation projects and is commonly used to monitor pushbuttons, limit switches, proximity sensors, and other 24 V devices on manufacturing lines or process-control setups. The 16‑channel DI configuration fits within the SM321 family, and the part is identified by 6ES7 321-1BH02-0AA0 (also cataloged as 6ES7321-1BH02-0AA0), making it a familiar upgrade or replacement option for older S7-300 installations requiring additional digital inputs.