| Product Type | S7-300 Digital Extension |
| Product Model | 6ES7321-1CH20-0AA0 |
| Supply Voltage Type | DC |
| Product Dimensions | 40 MM × 125 MM × 120 MM |
| Power Supply Voltage | Rated value (DC) 48 V Allowable range, lower limit (DC) 48 V Allowable range, upper limit (DC) 125 V |
| Weight | 200 g |
High-Performance Digital Input Module for S7-300 Series: Model SM 321 or DI 16x24VDC, a standard signal module (SM) in the SIMATIC S7-300 PLC system—provides 16 channels of DC digital inputs for acquiring field switch signals such as pushbuttons, limit switches, and relay contacts.
High-Density Design, Space-Saving:Expands 16 digital inputs in just one S7-300 slot, compact and ideal for systems requiring dense I/O configurations.
16-Channel 24 V DC Source Input:Supports standard 24 V DC PNP-type sensor inputs (high-side active), compatible with most industrial proximity sensors, photoelectric switches, and mechanical contacts.Each channel features optical isolation for enhanced noise immunity
Advanced Diagnostic Capabilities:Supports channel-level diagnostics, including detection of broken common return lines (e.g., M-wire break).Individual LED indicators per channel show real-time ON/OFF status.Diagnostic data accessible via STEP 7 software for remote monitoring and troubleshooting.
Broad Application Compatibility: Widely used in manufacturing automation, packaging machines, conveyor systems, and process control—serving as a fundamental component for building robust and reliable PLC control systems.
