The 1785-LTR controller is a classic programmable controller from the 1785 series by Allen-Bradley. This controller is meant to be used in systems that have been designed to have centralized control in a distributed control system. Centralized control is a system where the control over an entire application process is concentrated in one processor. These controllers enable the users to have quick access to the switches, status bits, indicators, instructions, and SW screens. To install the Allen-Bradley 1785-LTR classic programmable controller in a classic PLC-5 controller system, it is necessary to select the proper hardware components and determine the necessary features of the classic processor to make sure it is compatible with the controller system. Once all the controller specifications have been determined, the classic PLC-5 system layout can be planned and constructed.

The Allen-Bradley 1785-LTR classic programmable controller belongs to Series A of the PLC-5 prodduct line and it has a maximum user memory capacity of 6,000 words that is expandable to 10,000 or 14,000 words depending on the application. This controller also features an EEPROM module with a capacity of 8,000 words. The maximum number of analog I/O for this module is 512 and it has a scan time per thousand words of 2 milliseconds with discrete logic and 8 milliseconds with a typical application. The Allen-Bradley 1785-LTR classic programmable controller comes with 1 DH port and 1 Remote I/O port that includes an adapter or a scanner. It has 4 I/O racks and 13 I/O chassis in total. The remote I/O transmission rates go up to 57.6 KB per second and it has a backplane current load of 2.5 Amps.