Original General Order 95 

Section VIII

Detailed Construction Requirements for Communication Lines
(Class C Circuits) 

89.3    Telephone Instruments on Poles or Structures

Where a telephone instrument is attached to the surface of a pole or structure at less than 8 feet vertically above the ground (or at any elevation on a grounded metal pole or structure) and is connected to a private communication circuit constructed on the same pole line with, or colinear with, a Class H supply circuit, or is connected to a private communication circuit carried on crossarms with supply conductors of 750-20,000 volts, such instrument shall be enclosed in a suitable box of wood or equivalent insulating material, which shall be locked to prevent access by unauthorized persons. Where such a telephone instrument is so attached, connected, and enclosed, unless isolated from the communication circuit by an adequate insulating transformer, a suitably insulated stool or platform, on which a person can stand while using the instrument, shall be provided.