The excerpt discusses the advantages of Programmable Logic Controllers (PLCs) in automation systems. PLCs store control software locally, consist of a CPU with a microprocessor, memory chip, and integrated circuits for communication. PLCs follow a sequence of input scan, program scan, program logic execution, output update, and housekeeping for self-diagnostics. Relays are used to control other relays in forming logic controllers, like in the case of an AND gate where two inputs need to be energized for the output to activate. PLCs play a crucial role in automating processes by scanning inputs, executing programmed logic, and updating outputs accordingly.