can any give a simple difference between class 1 ,class 2,class 3 circuits ? art # 725 is almost impossible to understand. and where to apply each class ?

The difference is that Class 1 will say Class 1 on the device, Class 3 will say Class 3 etc.

There is no way for you to determine the class of wiring anymore. It is supposed to be printed on all listed transformers and power supplies.

-Hal

unforeteally ,, the low voltage cables they do have class type stamped on it. is is very common with thermosat wires and intercom wires they will have wire size , numbers of conducter, type and class if have it .

merci , marc