The Train Control and Monitoring System (TCMS) is the communication command center of the train. and the Central Control Unit (CCU) is its core component. which should achieve SIL4 safety integrity level defined in standard EN50129. Comparing the current CCU safety mode of dual-machine hot standby to the double 2 out of 2 (2oo2) structure. https://www.markbroyard.com/hot-save-turbo-air-m3f24-1-n-29-wide-m3-series-reach-in-freezer-featuring-one-solid-door-energy-star-on-sale-top-super/