 As 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.Early Simatic devices were transistor-based, intended to replace relays attached and customized to a specific machine.Microprocessors were introduced in 1973, allowing programs
similar to those on general-purpose digital computers to be stored and used for machine control.