AT&T 3.0 manual Central Office Trunk Protection

AC Power and Grounding

■Concrete-Encased Ground. Must be an electrode, consisting of one of the following:

At least 20 ft. (6.1 m) of one or more steel reinforcing rods, each at least ½ in. (1.27 cm) in diameter

20 ft. (6.1 m) of bare copper conductor not smaller than #4 AWG, encased in 2 in, (5 cm) of concrete

This electrode must be located within and near the bottom of a concrete foundation or footing that is in direct contact with the earth.

Ground ring, consisting of at least 20 ft. (6.1 m) of bare copper conductor (not smaller than #2 AWG) encircling the building. The ground ring must be in direct contact with the earth and buried at least 2.5 ft. (77 cm) below the earth’s surface.

WARNING:

Do not use a metal underground gas piping system—this is a safety risk.

Central Office Trunk Protection

The telephone company is responsible for providing the following protection of central office (co) trunks at the entrance to the site:

■Carbon blocks or gas discharge tubes connected to an approved ground

■Adequate bonding of the central office trunk protector ground and the power company ground

CAUTION:

Check these requirements with a simple, visual inspection. If you cannot verify that the central office grounding requirements are met, contact the central office. Do not connect the control unit to the central office trunks until you are certain that these requirements are met.

Installing the Control Unit 2-13