The Allen Bradley PLC has been around for years, and gone through several families of processors, cases and logic upgrades. Most older plants have Allen Bradley PLC's whether it is the Allen Bradley SLC, the Allen Bradley PLC-2 or older. Due to the robust nature of the Allen Bradley brand, or the ease of use in programming the Allen Bradley PLC's, it has maintained its dominance in several markets. The best place to buy Allen Bradley PLC's is though PLC outlet, which gives a dynamic view of the surplus Allen Bradley market.