2021603 is a part number for a Siemens SIMATIC S7-200CPU221 and S7-204 CPU programmable logic controller. This PLC is used to automate process control and machine control applications. It includes five digital inputs, two analog inputs, two temperature inputs, four digital outputs, two analog outputs, and a 256K memory for programming and data storage. It also features numerous ASICs, Ethernet, PC/104 expansion, and programming software. It is suitable for industrial control automation solutions, such as factory automation, process control, motion control, machine control, motor control, and more.