The Siemens 6ES7321-1BL00-0AA0 is a digital input module from the SIMATIC S7-300 series, designed for industrial automation applications. This module, SM 321, provides 32 digital inputs to interface with sensors, switches, and other field devices, converting their signals for the S7-300 PLC system. It operates on a 24V DC supply and features optical isolation to protect the PLC’s internal circuitry from external electrical noise and surges. Its high channel density makes it a space-efficient and cost-effective solution for expanding the input capabilities of a control system. A 40-pin front connector is required for wiring.