1756-L72S sequential actions according to logical conditions, and control of interlocking protective actions according to logical relationships, and data acquisition of large numbers of discrete quantities. Traditionally, these functions are achieved through pneumatic or electrical control systems.HCU37003703E is based on integrated circuits and electronic technology control devices, the first time the use of programmed means applied to electrical control, which is the first generation of programmable controllers, called Programmable Controller (PC).

After the development of personal computers (referred to as PC), for convenience, 1756-L72S also in order to reflect the functional characteristics of programmable controllers, programmable controllers named Programmable Logic Controller (PLC), and now, still often PLC referred to as PC. programmable controllers and their related equipment should be easy to form an integrated, easily expandable control system with the industry. Programmable Logic Controller and its related devices should be designed according to the principle of easy to form a whole with industrial control system and easy to expand its functions.

The 1756-L72S is a digital algorithmic electronic system designed for use in industrial environments. It employs a programmable memory for storing instructions to perform logical operations, sequence control, timing, counting, and arithmetic operations within it, and to control various types of machinery or production processes through digital and analogue inputs and outputs.