waross, you need to get a more recent version of NEC, thanks for your help.
From NEC 2005:
725.1 This article covers remote-control, signaling, and power-limited circuits that are not an integral part of a device or appliance.
The difficulty I am having is determining if an industrial control circuit is within the scope of 725. Is it a device?
Further in the General Discussion section, I find the following:
Class 1 remote-control circuits are commonly used to operate motor controllers in conjunction with moving equipment or mechanical processes, elevators, conveyors, and other such equipment. Class 1 remote-control circuits may also be used as shunt trip circuits for circuit breakers. Class 1 signaling circuits often operate at 120 volts but are not limited to this value.
None of the circuits I am considering have motor controlers, nor conveyors, however is an assembly system considered a mechanical process?
As you can see the matter is quite confusing and in deciding that compliance with class 2 is required we will have to double power supplies in the assembly system.