Siemens PLCs - Programmable Logic Controllers 6ES7521-7BH00-0AB0Siemens, SIMATIC S7 1500, digital input module DI 16x24 V DC AUX; 16 channels in groups of 8; for 24 V encoder; sensor supply 24 V DC; input type 2 (IEC 61131); input delay parameterizable 0. 05.. 20 ms; isochronous mode up to 250 s; integrated counting function up to 20 kHz; pulse stretching; chatter monitoring; signal inversion diagnostics; hardware interrupts: front connector (screw terminals or push in) and, if applicable, order shield set