Siemens 6ES7321-1BL00-0AA0 SIMATIC S7-300 Digital Input SM 321
The Siemens 6ES7321-1BL00-0AA0 is a high-density digital input module for the SIMATIC S7-300 automation system. It gives you 32 isolated 24V DC digital inputs on a single module, arranged in 4 groups of 8, making it a solid choice when you need to bring a lot of field signals, pushbuttons, limit switches, sensors, into your PLC without using up multiple slots. It's officially listed by Siemens as a spare part, and it works in both centralized S7-300 racks and distributed ET 200M I/O stations.