The 1756-L71 is a ControlLogix scalable controller that can handle a large amount of I/O points. It is compatible with ControlLogix I/O chassis and numerous others controllers. It is capable of monitoring and controlling ControlLogix backplane and network I/O's. The controller is capable of addressing 32 tasks and 100 programs per task. There is one USB port available for communication with additional options for other process and device networks. It supports up to five hundred controller connections. The model 1756-L71 has 2 megabytes user memory and 0.98 megabytes I/O memory with an option of nonvolatile memory storage of 1 or 2 gigabytes.

The maximum total digital I/O is 128,000 and analog I/O is 4000. It draws 5 milliamperes current at 1.2 Volts Direct Current and 800 milliamperes at 5.1 Volts Direct Current. The power dissipation is 2.5 W with a heat dissipation rate of 8.5 British Thermal Units (BTU) per hour. The isolation voltage is 30 volts continuous with basic insulation and USB port-to-system is tested at 500 Volts Alternate Current for 60 seconds. The approximate weight is 0.25 kilograms (0.55 pounds). The controller works in the temperature range of 0 to 60 degrees Celsius (32 to 140 degrees Fahrenheit) and can be stored at -40 to 85 degrees Celsius (-40 to 185 degrees Fahrenheit) with a relative humidity of 5% to 95%, non-condensing. The robust unit can tolerate vibrations of up to 2 g at 10 to 500 Hertz frequency, as well as shock of 30 g while operating and 50 g when out of service.

The Allen-Bradley 1756-L71 is part of the ControlLogix Series A of automation controllers. This controller has 2 MB of user storage memory and 0.98 MB of I/O memory, and an integrated 4-character alphanumeric panel for convenient inspection of the controller abnormalities and run-time data. The user only needs to create a program element and choose the logical channel where the I/O is physically linked with 1756-L71. This function allows for a speedier start and program familiarisation. In certain PLCs, the user may be required to transfer a registration from one to another in order to commence conversion and processing in order to obtain analog data. The user has to determine the logical channel where the I/O signal is physically terminated to utilize this controller. Along with an open enclosure and one full-speed USB port, the controller can also provide conditional controller redundancy. Moreover, the controller has the ability to handle up to 128,000 discrete input and output signals as well as 4000 analog input and output signals. This contemporary controller uses energy storage modules with the catalog numbers 756-ESMCAP or 1756-ESMCAPK to retain the contents of the RAM instead of batteries. The 1756-L71 comes with three capacitor modules for energy storage, two of which are detachable and the third, the non-removable, restricts USB connections to safeguard the controller. The controller provides a non-volatile memory option namely the 1784-SD1 which is a 1GB SD card. (expandable by 2 GB). Because the diagnostic data is recorded on the SD card, it is critical that it stays attached to the controller.