Many machines used in automated manufacturing environments in the early 1970's had rotary cam switches or limit switches to sense machine position and used hard-wired relay control panels to control machine operation. Even the smallest change in machine control logic required extensive work to modify the relay control panel. New control development was very inefficient since each control logic required custom-built hardware. Further, adjusting a machine's cam settings for a new set-up required many hours or even days of machine down-time.

The mid 70's saw the development of new controls to solve these problems. Programmable Logic Controllers (PLCs) were developed to replace the relay control panels and AVG Automation invented an electronic Programmable Limit 

Switch (PLS) to replace the mechanical, cam tripped, limit switches. The PLS consists of an absolute-position transducer, mounted in place of the rotary cam limit switch, and programmable electronics mounted in the control panel. With the advent of the PLS, cam settings can be altered in minutes instead of hours. Also, cam settings can be optimized by fine­tuning while a machine is in operation.

The PLS and PLC combination has been so successfully employed in factory automation that it is now standard for many kinds of machines. The PLS, because of its speed and accuracy, controls high-speed machine operations with precision and can provide the PLC accurate timing, position, or RPM data. The PLC controls slower machine functions and provides overall machine control.