This article is about Telecommunications Entrance Facility as per international standard codes J-STD-607-A for telecom engineers, technicians and supervisors.
Telecommunications Entrance Facility
The telecommunications entrance facility (TEF) is the entry point where all telecommunications facilities enter a building, including the joining of inter- and intrabuilding backbone facilities and grounding (earthing) of these facilities. Additionally, the TEF may include antenna cable entrances and electronic equipment serving telecommunications functions.
To ensure the best functionality of the TEF, it is desirable that all utilities enter the building in close proximity to each other. Here are some guidelines for placing the telecommunications main grounding busbar (TMGB) and other attachments to the TMGB in the Telecommunications Entrance Facility.
Placing the Telecommunications Main Grounding Busbar (TMGB)
The TMGB is the desirable location for grounding busbars in the TEF. It is the common point for all telecommunications grounding connections in that room or space. Therefore, it is essential to place the TMGB as close as practicable to the panelboard for telecommunications equipment and maintain the clearances required by applicable electrical codes.
If a panelboard for telecommunications equipment is not installed in the Telecommunications Entrance Facility, the TMGB should be located near the backbone cabling and associated terminations. Additionally, the TMGB should be located so that the bonding conductor for telecommunications is as short and straight as possible.
Other Attachments to the TMGB
The primary protector grounding conductor must be connected to the TMGB, intended to conduct lightning and ac fault currents from the telecommunication primary protectors. A minimum of 300 mm (1 ft) separation must be maintained between this insulated conductor and any dc power cables, switchboard cable, or high frequency cables, even when placed in rigid metal conduit or EMT.
When the outside plant cables in the TEF incorporate a cable shield isolation gap, the cable shield on the building side of the gap must be bonded to the TMGB. In buildings where the backbone cable incorporates a shield or metallic member, this shield or metallic member must be bonded to the TMGB or TGB.
Telecommunications primary protectors for the interbuilding backbone cables must be bonded to the TMGB. All metallic pathways for telecommunications cabling located within the same room or space as the TMGB shall be bonded to the TMGB. However, for metallic pathways containing grounding conductors where the pathway is bonded to the grounding conductor, no additional bond to the TMGB is required.
Other Grounding Busbars
The TMGB is intended to be the location for connecting grounding busbars incorporated in telecommunications equipment located in the Telecommunications Entrance Facility (TEF) (e.g., multiplexer or optical fiber termination equipment).
Other Service Entrances
Where antenna cables enter a building, the point of entry should be treated as an entrance facility. Where an entrance facility is located at the roof, a TGB shall be provided in accordance with entrance facility requirements.
In conclusion, proper grounding and bonding are essential for the proper function and safety of telecommunications facilities. Understanding the requirements for the TEF, TMGB, and other attachments is critical to ensuring that the system operates correctly and meets industry standards.
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