Definitions of Terms as Used in The Rules of This Order
20.5 Circuit means a conductor or system of conductors located outside of buildings and through which an electric current is intended to flow.
A. Class C Communication Circuits mean circuits which are used for public or private communication service and which operate at not exceeding 400 volts to ground nor 750 volts between any two points of the circuit and the transmitted power of which does not exceed 150 watts. When operated at less than 150 volts no limit is placed on the capacity of the system.
Note Telephone, telegraph, messenger-call, clock, fire or police alarm circuits are included in this classification and other circuits used for signal purposes in which the above limitations are not exceeded may be included.
(1) Major Class C Circuits mean communication circuits which include the following:
More than four conductors (open, paired or in cable) used chiefly for local exchange service.
Toll telephone or telegraph circuits used for transmission of messages of the general public, and not including clack, messenger call, railway signal, police, fire alarm and other special communication circuits.
(2) Minor Class C Circuits mean communication circuits not installed in the definition of Major Class C Circuits. (see Rule 20.5-A1.)
B. Private Communication Circuits mean circuits used for private communication, signal or control service in the operation of other facilities. (see Rules 78.2 and 89.)
Railway Signal Circuits mean
those supply and communication circuits used primarily for supplying energy for
controlling the operation of railway block signals highway crossing signals,
interlocking apparatus and their appurtenances.
Circuits which operate at less than 400 volts to ground are considered as communication (Class C) circuits and shall be so classified and treated provided that, if the voltage exceeds 150 volts between conductors the power transmitted shall not exceed 150 watts. Where all circuits of a line are owned and operated by one utility, the voltage between conductors carrying in excess of 150 watts may be increased to not more than 250 volts and the signal circuits may be considered as communication (Class C) circuits.
All railway signal circuits which do not meet the requirements above shall be treated as supply circuits of corresponding voltage.
D. Supply Circuits mean those circuits which are used for transmitting a supply of electrical energy.
(1) Class H Circuits include the following:
Constant potential alternating current circuits of 5000 volts or more between any two conductors
Constant potential alternating current circuits of 2900 volts or more between any conductor and ground
Constant potential direct current circuits exceeding 750 volts between any conductor and ground
Constant current circuits of 7.5 amperes or less supplied from transformers or devices having a normal full-load output voltage of 5000 volts or more
Constant current circuits of more than 7.5 amperes supplied from transformers or devices having an open-circuit voltage of 2900 volts or more.
(2) Class L Circuits include the following:
Constant potential alternating or direct current supply circuits of lower voltage than Class H
Constant current circuits of 7.5 amperes or less supplied from transformers or devices having a normal full-load output voltage less than 5000 volts
Constant current circuits of more than 7.5 amperes supplied from transformers or devices having an open-circuit output voltage less than 2900.
E. Class T Circuits mean trolley contact conductors, feeder wires and other conductors metallically connected to such contact conductors, used in electric railway or trolley operation. These Class T circuits are supply circuits, further classified as Class L or Class H depending upon the voltage and nature of current used (see Rule 20.5-D)