32    Classification For Clearnaces.

(a)    For the purposes of determining clearances and spacings (see Section IV), supply circuits are classified according to voltage carried (see Definition 17(g)), except that constant current series lighting circuits will be treated as follows throughout the rules:

1.    Constant current series lighting circuits, where the maximum working voltage between the conductors at the terminals of the constant current series transformer of generator supplying the circuit does not exceed 750 volts, will be treated as supply lines 0 to 750 volts.

Such low voltage circuits are sometimes obtained by the use of insulating transformers on high voltage series circuits.

2.    All constant current series circuits of higher voltage than the above will be treated as Class “L” circuits, except that circuits of this character having normal currents exceeding 7.5 amperes shall be classified as Class “H” circuits.

(b)    Signal circuits, for purposes of clearance, are classed exactly, as in Rule 31.