What are the major PLC hardware components?

Remember that a chassis is what's used to host your cards, the backplane is the medium over which the cards communicate and the slot refers to their position

Mitsubishi Melsec A35B IO PLC Base Unit Rack 5-Slots A-35B IO Chassis: : Industrial & Scientific

grondanker slot Rack is cabinet for placing the modules It comes in a different sizes like 9 slots,18 slots, etc Modular PLC Rack with slots PLC Chassis:

book of vampires slot 6ES7401-2TA00-0AA0 € Siemens Simatic S7-400 6ES7401-2TA00-0AA0 CR2 RACK, CENTRALIZED,18 SLOTS,2 SEGMENTS rack, plc rack, rack, s7-400, simatic,