Pennsylvania Code
Title 34 - LABOR AND INDUSTRY
Part I - Department of Labor and Industry
Chapter 39 - SAFETY STANDARDS-GENERAL
Subchapter B - ELECTRIC SAFETY
TELEPHONE AND OTHER SIGNAL APPARATUS ON CIRCUITS EXPOSED BY SUPPLY LINES
Section 39.302 - Guarding current-carrying parts

(a) Telephone or other signaling devices which are permanently located outdoors or if exposed to corrosive fumes or dampness, such as may occur in subways, cellars, basements, laundries, stables, and the like, shall be so arranged that ungrounded current-carrying parts are guarded so as to be suitably protected against the prevailing atmospheric conditions. The enclosing cases of signal apparatus provide suitable guards if substantially built of metal or insulating material.

(b) Receiver cords shall be guarded by shields of permanently grounded metal, such as metal armor, or of nonabsorptive insulating material, such as flexible insulating tubing, or shall have suitable insulating coverings for the individual conductors.

(c) If no protective device is installed the shields of portable cords shall always be of grounded metal or of special insulating material suitable to withstand the voltage of the highest supply circuit to which the signal circuit is exposed up to 7,500 volts. Only for fire-alarms or similar apparatus or for apparatus not for public use, where the character of service precludes the use of arresters and fuses, is a lack of a protective device be permissible.