Microprocessors were introduced in 1973, allowing programs similar to those on general-purpose digital computers to be stored and used for machine control. Simatic devices have input and output modules to connect with controlled machines. Early Simatic devices were transistor-based, intended to replace relays attached and customized to a specific machine. Siemens Simatic S7-300 PLC CPU with three I/O modules attachedĪs with other programmable logic controllers, Simatic devices are intended to separate the control of a machine from the machine's direct operation, in a more lightweight and versatile manner than controls hard-wired for a specific machine.
