The Siemens 6ES7 231-OHC22-0XA8 is a SIMATIC S7-200 series analog input module, model EM 231. This expansion module is specifically designed to work with S7-22X CPUs, enabling the programmable logic controller to process analog signals from various sensors. It features four high-resolution analog inputs, primarily for connecting thermocouples of multiple types (J, K, S, T, R, E, N) or voltage signals up to +/-80mV. This module is an essential component for applications requiring precise temperature measurement and control in legacy industrial automation systems, offering reliable and accurate data conversion for process monitoring.