Siemens 6ES7321-1BH50-0AA0 Digital Input Module

Siemens 6ES7321-1BH50-0AA0 is a SIMATIC S7-300 digital input module (SM 321) that provides 16 DC 24 V input channels with galvanic isolation from the backplane. Designed for source-input configuration, each input is fed by a +24 V DC source and delivers a clean logic signal to the S7-300 CPU. The module mounts in a standard S7-300 rack and uses a single 20-pole interface for the backplane connection. Typical applications include reading 24 V DC signals from switches, sensors, and safety devices in automation systems where compact, reliable digital inputs are required. Key specifications include 16 digital inputs, 24 V DC input voltage, source-input configuration, galvanic isolation, and a 20-pole connector. The documented response time is up to 1.2 ms, suitable for mid-speed digital sampling in control tasks. This SM 321-based module is ideal for expanding legacy S7-300 installations, offering straightforward integration with existing PLC programs and I/O configurations.