6ES7321-1BL00-0AA0Overview The Siemens 6ES7321 1BL00 0AA0 is a digital input module from the SIMATIC S7 300 series. It offers 32 isolated digital inputs operating at 24 V DC. Designed for industrial automation, this SM 321 module connects via a 40 pin front connector and supports a wide range of standard input devices. Key Features 32 digital inputs, isolated in groups of 16 Rated input voltage: 24 V DC Compatible with 2 , 3 , and 4 wire proximity switches (BEROs)