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Subchapter 20. Tunnel Safety Orders
Article 9. Emergency Plan and Precautions
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§8428. Telephone System.

(a) Communications

(1) During periods of major construction or repair, tunnels that will be more than 2,000 feet long shall have at least one underground telephone as soon as the length reaches 1,000 feet. Other phones are to be added as the work progresses so that there is never less than one phone to serve each length-zone of 2,000 feet, and one for any remaining zone exceeding 1,000 feet in length. They shall be conveniently located and properly identified. Arrangements shall be such that calls will be answered promptly. A telephone or communication system shall be provided when more than 5 employees are underground.

(2) When natural unassisted voice communication is ineffective, a power assisted means of voice communications shall be used to provide communications between the workface, the bottom of the shaft and the surface.

(b) Telephone systems shall be independent of the tunnel power supply and shall be installed so that the destruction of one telephone will not interrupt the use of other telephones on the same system.

(c) Telephones shall be equipped with an audible or visual signal suitable for the conditions present and capable of adequately alerting the employees of an in-coming call. Equivalent communication systems may be used when accepted by the Division.

(d) Communication systems shall be tested upon initial entry of each shift to the underground, and as often as necessary at later times, to ensure that they are in working order.

(e) Telephone and low potential signal wire shall be protected from contacting energized power conductors or any other power source by isolation or suitable insulation, or both.

NOTE: Authority cited: Sections 142.3 and 7997, Labor Code. Reference: Sections 142.3 and 7997, Labor Code.


1. Amendment of section and new Note filed 3-5-96; operative 4-4-96 (Register 96, No. 10).

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