Uticor, formerly Struthers Dunn Systems division, has been in the forefront of PLC Technology since late 60's even though Modicon is generally credited for the invention of PLCs in a General Motors Plant in Detroit, the fact is that
Uticor was one of the early inventors of PLCs back in 1968. It held numerous patents on PLCs, then called Process Control Computers.
Uticor did not market its process control computers as independent PLC products. Instead these process control computers were used as sub systems in the automotive and electric utility companies.
In the 1970's, Uticor applied it's PLC technology to welding controls and became one of the top suppliers of this technology to the Automotive industry. In fact, Uticor provided university research grants in collaboration with Ford in this area.